Fix an incorrect auto-correct for Style/RedundantReturn

[koic]

Fixes standardrb/standard#277.

This PR fixes the following false positive for Style/RedundantReturn when using return with splat argument.

% cat example.rb
class MyClass
  def something
    data = [1, 2, 3]
    return *data
  end
end

Before

Auto-corrected to invalid code.

% rubocop --only Style/RedundantReturn -a
(snip)

% cat example.rb
class MyClass
  def something
    data = [1, 2, 3]
    *data
  end
end

% ruby -c example.rb
example.rb:4: syntax error, unexpected '\n', expecting '='

After

Auto-corrected to valid code.

% rubocop --only Style/RedundantReturn -a
(snip)

% cat example.rb
class MyClass
  def something
    data = [1, 2, 3]
    data
  end
end

% ruby -c example.rb
Syntax OK

---

Before submitting the PR make sure the following are checked:

• The PR relates to only one subject with a clear title and description in grammatically correct, complete sentences.
• Wrote good commit messages.
• Commit message starts with [Fix #issue-number] (if the related issue exists).
• Feature branch is up-to-date with master (if not - rebase it).
• Squashed related commits together.
• Added tests.
• Ran bundle exec rake default. It executes all tests and runs RuboCop on its own code.
• Added an entry (file) to the changelog folder named {change_type}_{change_description}.md if the new code introduces user-observable changes. See changelog entry format for details.

[searls]

Your responsiveness is truly amazing, @koic!

[bbatsov]

Yep, @koic is a legend! Thanks! 🙇‍♂️