Re-enable Layout/SpaceAroundOperators cop

[kamipo]

We prefer space around operators, but Layout/SpaceAroundOperators cop
was temporarily disabled in #36943 since that cop changed to check
alignment strictly somehow.

In RuboCop 1.0.0, that is fixed by rubocop/rubocop#8906.

Related #38034 (comment), #39770 (comment).

[kamipo]

There is EnforcedStyleForExponentOperator configurable attributes, but here is only line that space around exponent operator, so I'll accept this change.

https://docs.rubocop.org/rubocop/1.0/cops_layout.html#configurable-attributes-41

% git grep -n ' \*\* '
activemodel/lib/active_model/type/helpers/time_value.rb:78:              usec *= 10 ** (6 - usec_len)
railties/lib/rails/commands/secrets/USAGE:1:=== ** DEPRECATED **

% git grep -n '[a-z0-9]\*\*[a-z0-9]'
actionpack/test/controller/parameters/parameters_permit_test.rb:62:    values += [0, 1.0, 2**128, BigDecimal(1)]
Binary file actiontext/test/fixtures/files/racecar.jpg matches
actionview/test/template/date_helper_test.rb:194:    assert_equal "about 3 years", distance_of_time_in_words(10**8)
actionview/test/template/date_helper_test.rb:195:    assert_equal "about 3 years", distance_of_time_in_words(0, 10**8)
actionview/test/template/number_helper_test.rb:117:    assert_equal "100&lt;script&gt;&lt;/script&gt;000 Quadrillion", number_to_human(10**20, delimiter: "<script></script>")
actionview/test/template/render_test.rb:157:    assert_equal "4", @view.render(inline: "(2**2).to_s", type: :ruby)
activejob/lib/active_job/exceptions.rb:26:      #   <tt>:exponentially_longer</tt>, which applies the wait algorithm of <tt>((executions**4) + (Kernel.rand * (executions**4) * jitter)) + 2</tt>
activejob/lib/active_job/exceptions.rb:137:          delay = executions**4
activemodel/lib/active_model/type/helpers/time_value.rb:28:          round_power = 10**number_of_insignificant_digits
activemodel/test/cases/validations/length_validation_test.rb:166:    bigmin = 2**30
activemodel/test/cases/validations/length_validation_test.rb:167:    bigmax = 2**32
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:588:          m.register_type %r(tinytext)i,   Type::Text.new(limit: 2**8 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:589:          m.register_type %r(tinyblob)i,   Type::Binary.new(limit: 2**8 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:590:          m.register_type %r(text)i,       Type::Text.new(limit: 2**16 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:591:          m.register_type %r(blob)i,       Type::Binary.new(limit: 2**16 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:592:          m.register_type %r(mediumtext)i, Type::Text.new(limit: 2**24 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:593:          m.register_type %r(mediumblob)i, Type::Binary.new(limit: 2**24 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:594:          m.register_type %r(longtext)i,   Type::Text.new(limit: 2**32 - 1)
activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb:595:          m.register_type %r(longblob)i,   Type::Binary.new(limit: 2**32 - 1)
activerecord/lib/active_record/fixtures.rb:464:    MAX_ID = 2**30 - 1
activerecord/test/cases/bind_parameter_test.rb:112:        topics = Topic.where(id: (1 .. bind_params_length).to_a << 2**63)
activerecord/test/cases/bind_parameter_test.rb:115:        topics = Topic.where.not(id: (1 .. bind_params_length).to_a << 2**63)
activerecord/test/cases/migration_test.rb:391:      world_population: 2**62,
activerecord/test/cases/migration_test.rb:406:    assert_equal 2**62, b.world_population
activerecord/test/cases/numeric_data_test.rb:22:      world_population: 2**62,
activerecord/test/cases/numeric_data_test.rb:33:    assert_equal 2**62, m1.world_population
activerecord/test/cases/numeric_data_test.rb:49:      world_population: 2**62,
activerecord/test/cases/numeric_data_test.rb:60:    assert_equal 2**62, m1.world_population
activerecord/test/cases/numeric_data_test.rb:77:        world_population: 2**62,
Binary file activestorage/test/fixtures/files/racecar.jpg matches
Binary file activestorage/test/fixtures/files/racecar.tif matches
Binary file activestorage/test/fixtures/files/racecar_rotated.jpg matches
Binary file activestorage/test/fixtures/files/video.webm matches
activesupport/lib/active_support/key_generator.rb:16:      @iterations = options[:iterations] || 2**16
activesupport/lib/active_support/number_helper/number_to_human_converter.rb:26:        @number = number / (10**exponent)
activesupport/lib/active_support/number_helper/number_to_human_size_converter.rb:24:          human_size = number / (base**exponent)
activesupport/test/core_ext/numeric_ext_test.rb:107:    assert_equal 1.kilobyte**4, 1.terabyte
activesupport/test/core_ext/numeric_ext_test.rb:111:    assert_equal 1.kilobyte**5, 1.petabyte
activesupport/test/core_ext/numeric_ext_test.rb:112:    assert_equal 1.kilobyte**6, 1.exabyte
activesupport/test/core_ext/numeric_ext_test.rb:383:    assert_equal "100000 Quadrillion", (100**10).to_s(:human)
activesupport/test/core_ext/numeric_ext_test.rb:390:    assert_equal "100000000000000000000", (100**10).to_s(:invalid)
activesupport/test/core_ext/numeric_ext_test.rb:400:    assert_equal "100000000000000000000", (100**10).to_s
activesupport/test/core_ext/numeric_ext_test.rb:401:    assert_equal "1010110101111000111010111100010110101100011000100000000000000000000", (100**10).to_s(2)
Binary file guides/assets/images/association_basics/has_one_through.png matches
Binary file guides/assets/images/getting_started/rails_welcome.png matches
guides/source/active_support_core_extensions.md:2045:[].sum(1) {|n| n**3} # => 1