Suppress RuboCop's offense

This PR commit suppresses and auto-corrects the following RuboCop's offense.

```console
% bundle exec rubocop -a
Inspecting 70 files
...................W..................................................

Offenses:

lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:13:52:
C: [Corrected] Style/RedundantBegin: Redundant begin block detected.
          self.class.quoted_column_names[name] ||= begin
                                                   ^^^^^
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:14:11:
C: [Corrected] Layout/IndentationWidth: Use 2 (not 4) spaces for indentation.
              "\"#{name.upcase}\""
          ^^^^
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:15:13:
C: [Corrected] Layout/ElseAlignment: Align else with self.class.quoted_column_names[name].
            else
            ^^^^
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:16:15:
C: [Corrected] Layout/CommentIndentation: Incorrect indentation
detected (column 14 instead of 12).
              # remove double quotes which cannot be used inside quoted identifier
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:17:11:
C: [Corrected] Layout/IndentationWidth: Use 2 (not 4) spaces for indentation.
              "\"#{name.gsub('"', '')}\""
          ^^^^
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:18:13:
W: [Corrected] Layout/EndAlignment: end at 18, 12 is not aligned with
self.class.quoted_column_names[name] ||= if at 13, 10.
            end
            ^^^
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:19:1:
C: [Corrected] Layout/EmptyLinesAroundMethodBody: Extra empty line
detected at method body end.
lib/active_record/connection_adapters/oracle_enhanced/quoting.rb:19:1:
C: [Corrected] Layout/TrailingWhitespace: Trailing whitespace detected.

70 files inspected, 8 offenses detected, 8 offenses corrected
```

lib/active_record/connection_adapters/oracle_enhanced/quoting.rb

@@ -10,14 +10,11 @@ module Quoting
 
         def quote_column_name(name) #:nodoc:
           name = name.to_s
-          self.class.quoted_column_names[name] ||= begin
-            # if only valid lowercase column characters in name
-            if /\A[a-z][a-z_0-9$#]*\Z/.match?(name)
-              "\"#{name.upcase}\""
-            else
-              # remove double quotes which cannot be used inside quoted identifier
-              "\"#{name.gsub('"', '')}\""
-            end
+          self.class.quoted_column_names[name] ||= if /\A[a-z][a-z_0-9$#]*\Z/.match?(name)
+            "\"#{name.upcase}\""
+          else
+            # remove double quotes which cannot be used inside quoted identifier
+            "\"#{name.gsub('"', '')}\""
           end
         end