Small Action View Overview edits [ci skip]

Some small grammar and readability edits
Grammar pass

[ci skip]

Add improvements from @eileencodes [skip ci]
[ci skip] Added documentation for has_many scope parameter
Fix a few typos/some grammar in Active Job Basics
Merge pull request #16590 from loganhasson/master

[ci skip] Fix typos/grammar in Active Job guide
[ci skip] correct docs about the migration generation
Merge pull request #16592 from aditya-kapoor/fix-migration-docs

[ci skip] correct docs about the migration generation
[ci skip] add doc for STEP in migration
Merge pull request #16575 from tomkadwill/added_has_many_scope_documentation

[ci skip] Added documentation for has_many scope parameter
Merge pull request #16593 from aditya-kapoor/add-doc-for-step

[ci skip] add doc for STEP in migration
[ci skip] Fix Active Job grammar in api docs
Merge pull request #16594 from loganhasson/master

[ci skip] Fix Active Job grammar in api docs
Remove timestamp type from generator usage

It was soft removed at 03035d69e14032a589e9653e3145237b8a9a09be
Make the explicit the Active Job dependency of Action Mailer
Update configuring.md [ci skip]

Remove ActiveRecord config instructions for active_record.attribute_types_cached_by_default, which was removed in https://github.com/rails/rails/commit/66736c8e50585
Merge pull request #16597 from teeparham/master

Remove cached attributes from Configuring guide [ci skip]

This was removed in #15429
Fix SyntaxError
"warning: assigned but unused variable"
[ci skip] Fixing spelling typo in testing guide.
Merge pull request #16600 from bradly/spelling-fix-in-testing-guide

[ci skip] Fixing spelling typo in testing guide.