[ci skip] Correct output of Hash#symbolize_keys
Merge pull request #15448 from akshay-vishnoi/doc_changes

[ci skip] Correct output of Hash#symbolize_keys
[ci skip] correct doc for ActionView::Helpers::DebugHelper
Missing period from AP/CHANGELOG [ci skip]
Merge pull request #15449 from aditya-kapoor/correct-debug-doc

[ci skip] correct doc for ActionView::Helpers::DebugHelper
Removed 'Caching with Rails' guide from WIP, this guide isn't ready to
be published and requires more attention. [ci skip]