Updated doc for default scope [ci skip]
Tell default_scope are prepended [ci skip]
Aesthetic [ci skip]
Document the default scopes change on the release notes, CHANGELOG
and upgrating guides

[ci skip]
Fix the column name [ci skip]
Don't use `# =>` when it is not the expression values

[ci skip]
Merge pull request #14095 from rails/rm-scopes

Document `default_scope` changes