Up-to-date protobuf action should use authenticated requests

[StephenButtolph]

The buf check occasionally gets rate limited because we do not perform any authentication.

For example: https://github.com/ava-labs/avalanchego/actions/runs/9487445671/job/26144106471

See: https://docs.github.com/rest/overview/resources-in-the-rest-api#rate-limiting

[github-actions]

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