refactor: checkout homebrew-core in action instead of script (#4996)

* refactor: checkout homebrew-core in action instead of script

This moves the git clone step from the `brew-bump.sh` script into the
`npm-brew.yaml` as part of the job using actions/checkout instead.

* refactor: clean up brew-bump.sh script

* fixup

* fixup!: remove step to clean up homebrew repo

* fixup!: use correct ./ci path steps-lib.sh

* fixup!: add exit code 0 for duplicate PRs