Fixes #5480

See #5859

This removes the script which sets up the pre-commit hook and its corresponding script.

If you have this pre-commit script installed, you can remove it by deleting the .git/hooks/pre-commit file.

Steps for testing

1. Clone this repo
2. Switch to this branch
3. Run composer install
4. Confirm no pre-commit hook has been installed into .git/hooks/pre-commit
5. Commit some code that would normally fail coding standards checks
6. Confirm there's no error message and the commit succeeds