check-restricted-files.yaml: check for allowed PRs

Check in the whether the PR is an intra-repo sync PR or release PR and report "ok" for these.

Conditions:
- PR's `head` and `base` repo is `OAI/OpenAPI-Specification` and
  - `head` is `main` and `base` is `dev`, or
  - `head` is `dev` and `base` matches `v?.?-dev`, or
  - `head` matches `v?.?.?-rel` and `base` is `main`