Revert "Fix SyntaxError in guides sample code"

This reverts commit f573df32d43c413a5098721ba6151ff190c23c6c.

The original idea of this documentation was to showcase the feature
where you can remove some only queries attributes with a single
key-value pair.
remove duplication in test
Merge pull request #11491 from erichkist/ek-revert-unscope-patch

Revert "Fix SyntaxError in guides sample code"
Merge pull request #11492 from maratvmk/concern_test

remove duplication in concern_test
use the superclass implementation
fix typo in Active Record Validations guide. [ci skip].

Closes #11498.
Upgrade guide. Renaming Indexes on tables. [ci skip].

https://github.com/rails/rails/commit/39eef1a565ef02e4dabc0811ef1bf4547ff9a60e#commitcomment-3672522
Merge pull request #11501 from nishantmodak/patch-3

Upgrade guide. Renaming Indexes on tables. [ci skip]
Fix test name typos
Merge pull request #11507 from vipulnsward/av_typo-4

Fix test name typos