Run config_docs CI check is not run on PRs to only change generated docs (resulting in CI failures)

### Describe the bug

There are several times where we broke CI because we directly changed the .md markdown files that are autogenerated, but the CI in the PR did not run

Here are some recent-ish examples PRs that fixed such issues
- https://github.com/apache/datafusion/pull/19093
- https://github.com/apache/datafusion/pull/17026
- https://github.com/apache/datafusion/pull/17041

### To Reproduce

1. Make a PR with a change to a the docs in `docs/source/user-guide/sql/scalar_functions.md`
2. The CI will pass
3. Commit the PR

However then any PRs that run on code will fail because the autogenerated results will not match what is checked in.

Here is an example of a PR with such a mistake (and I should have known better 🤦 )
- https://github.com/apache/datafusion/pull/19088

### Expected behavior

let's fix the docs check to automatically run on PRs that change the auto generated files

### Additional context

_No response_

Use docs/source/user-guide/sql/scalar_functions.md as the reproduction case and inspect the CI entry point that runs the config_docs check, including its changed-path conditions. Confirm that a PR changing generated Markdown triggers the check and that the check still detects mismatched generated output.

Written by the indexing model from the issue text.