Enable Style/SymbolProc

What does this MR do?

This MR enables the Rubocop SymbolProc rule, which requires eta-conversion of blocks that take one argument and return the result of calling a method on that argument. i.e.:

things.select { |element| element.ok? }.map { |element| element.method }

Becomes:

things.select(&:ok?).map(&:method)

https://gitlab.com/gitlab-org/gitlab-ce/issues/62228

This MR will require activating the cop, and fixing any issues that subsequently arise.

Does this MR meet the acceptance criteria

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and testing

This has the potential to introduce bugs, so every line of code that is changed requires a test.

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers