Support AllCops:ActiveSupportExtensionsEnabled for Style/SymbolProc

[koic]

Follow up d39f073.

This PR supports AllCops:ActiveSupportExtensionsEnabled instead of a TODO comment in Style/SymbolProc cop.

---

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.

[bbatsov]

Thanks!

[etiennebarrie]

I'm seeing a false positive here with CSV converters. They also check the arity of the proc, so auto-correcting from ->(x) { x.upcase } to lambda(&:upcase) breaks. I guess it's fine because the autocorrect is not safe, but just wanted to point it out in case someone else hits this.

I was able to prevent Rubocop from reporting the offense by using the ActiveSupportExtensionsEnabled configuration option: Shopify/maintenance_tasks@d24e07a. Although I don't think this applies to everybody because a Ruby gem without Active Support could hit the same issue, but my case is a Rails engine so it's fine.