Ignore duplicate commit URLs from forked repositories

Some vulnerabilities contain multiple `commit_url` entries that reference the same commit hash in different repositories.

For example:
https://github.com/pypa/advisory-database/blob/main/vulns/requests/PYSEC-2015-17.yaml
https://public.vulnerablecode.io/advisories/pypa/requests/PYSEC-2015-17

The advisory contains the following commit URLs:

* https://github.com/kennethreitz/requests/commit/3bd8afbff29e50b38f889b2f688785a669b9aafc
* https://github.com/psf/requests/commit/3bd8afbff29e50b38f889b2f688785a669b9aafc

Both URLs point to the same Git commit (`3bd8afbff29e50b38f889b2f688785a669b9aafc`). The `kennethreitz/requests` repository is forked repository, while `psf/requests` is the current original repository.

To avoid duplicate patch commits, we should ignore commit URLs from forked repositories when the same commit is available in the original repository