feat: Remove hardcoded rule kinds requirement for source-code generators

[ghorak-happening]

Checklist

• [ ] I have filed an issue about this change and discussed potential changes with the maintainers.
• [ ] I have received the approval from the maintainers to make this change.
• [x] This is not a stylistic, refactoring, or cleanup change.

Please note that the maintainers will not be reviewing this change until all checkboxes are ticked. See the Contributions section in the README for more details.

Discussion thread for this change

Issue number: #6428

Description of this change

Removing hardcoded proto rule name to enable other Go code generators

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.