CodeQL GH workflow should be scoped only for source code changes

[somaritane]

As of now [CodeQL GH workflow ](https://github.com/k8gb-io/k8gb/blob/master/.github/workflows/codeql-analysis.yml workflow) is triggered for any change in the repository (e.g. documentation), which is suboptimal. It should be scoped only for source code changes.

[somaritane]

We're even hitting API rate limiting on CodeQL GH pipeline:

Error: API rate limit exceeded for installation ID 16862322.
RequestError [HttpError]: API rate limit exceeded for installation ID 16862322.

https://github.com/k8gb-io/k8gb/pull/488/checks?check_run_id=2574024211