Fix Style/MethodDefParentheses issue with splat forwarding

[bkuhlmann]

Expected behavior

I would expect Style/MethodDefParentheses to not throw errors when forwarding splats (single and double). This is similar in nature to this issue opened last year when anonymous block support was added to Ruby.

Actual behavior

You'll get the following errors when using splat forwarding:

/Users/bkuhlmann/Engineering/Misc/snippet:16:13: C: [Correctable] Style/MethodDefParentheses: Use def without parentheses. (https://rubystyle.guide#method-parens)
  def single(*)
            ^^^
/Users/bkuhlmann/Engineering/Misc/snippet:20:13: C: [Correctable] Style/MethodDefParentheses: Use def without parentheses. (https://rubystyle.guide#method-parens)
  def double(**)
            ^^^^

Steps to reproduce the problem

Start by configuring Rubocop to use the following configuration:

Style/MethodDefParentheses:
  EnforcedStyle: require_no_parentheses

Next, use the following code as an example:

module Demo
  def single(*)
    super
  end

  def double(**)
    super
  end
end

Save the above and run as rubocop snippet.rb and notice you get the same errors as reported above. If you were to remove the parentheses -- as RuboCop suggests -- then you'd get the following syntax error:

syntax error, unexpected `super', expecting ';' or '\n'
  15  module Demo
> 16    def single *
> 18    end
  23  end
/Users/bkuhlmann/Engineering/Misc/snippet:17: syntax error, unexpected `super', expecting ';' or '\n' (SyntaxError)
    super
    ^~~~~

RuboCop version

1.41.1 (using Parser 3.1.3.0, rubocop-ast 1.24.1, running on ruby 3.2.0) [arm64-darwin22.2.0]
  - rubocop-performance 1.15.2
  - rubocop-rake 0.6.0
  - rubocop-rspec 2.16.0
  - rubocop-thread_safety 0.4.4