[BazelBot] 429 on git fetch

[boomanaiden154]

Traceback (most recent call last):
  File "/var/lib/buildkite-agent/bazel-fixer-bot/./bazelbot_server_main.py", line 63, in <module>
    bot.run()
  File "/var/lib/buildkite-agent/bazel-fixer-bot/bazelbot_server.py", line 230, in run
    ] = self.build_processor.get_builds_to_process(self.last_processed_sha)
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/lib/buildkite-agent/bazel-fixer-bot/utils.py", line 339, in get_builds_to_process
    self.git_repo.refresh_main_branch()
  File "/var/lib/buildkite-agent/bazel-fixer-bot/utils.py", line 219, in refresh_main_branch
    self.repo.remotes.origin.fetch()
  File "/var/lib/buildkite-agent/bazel-fixer-bot/.venv/lib/python3.12/site-packages/git/remote.py", line 1076, in fetch
    res = self._get_fetch_info_from_stderr(proc, progress, kill_after_timeout=kill_after_timeout)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/lib/buildkite-agent/bazel-fixer-bot/.venv/lib/python3.12/site-packages/git/remote.py", line 902, in _get_fetch_info_from_stderr
    proc.wait(stderr=stderr_text)
  File "/var/lib/buildkite-agent/bazel-fixer-bot/.venv/lib/python3.12/site-packages/git/cmd.py", line 419, in wait
    raise GitCommandError(remove_password_if_present(self.args), status, errstr)
git.exc.GitCommandError: Cmd('git') failed due to: exit code(128)
  cmdline: git fetch -v -- origin
  stderr: 'fatal: unable to access 'https://github.com/google-bazel-bot/llvm-project.git/': The requested URL returned error: 429'

Maybe we want to be doing an authenticated clone?