fix(infra): create GitHub releases for partner package releases (#35234)

- GitHub releases have not been created for partner package releases
since #34784 (Jan 16). PyPI publishes were unaffected.

#34784 added `test-dependents` to the `publish` job's dependency chain.
`test-dependents` only runs for core/langchain releases, so it's skipped
for everything else. `publish` handles this with `if: ${{ !cancelled()
&& !failure() }}`, but `mark-release` (which creates the GitHub release)
doesn't have the same guard — so GitHub Actions skips it whenever
`test-dependents` is skipped.

## Missing GitHub releases
`langchain-xai==1.2.2`, `langchain-standard-tests==1.1.3`,
`langchain-groq==1.1.2`, `langchain-anthropic==1.3.2`,
`langchain-standard-tests==1.1.4`, `langchain-openai==1.1.8`,
`langchain-openai==1.1.9`, `langchain-anthropic==1.3.3`,
`langchain-openrouter==0.0.2`