Describe the bug, including details regarding any error messages, version, and platform.

Yet I am a committer.
RTFSing, I see that the job pulls https://raw.githubusercontent.com/apache/arrow-site/main/_data/committers.yml and then checks whether the current user is in the alias list there. But those aliases are apache IDs (historically, at least, and that's what mine is), not github usernames. They may be the same for some but not all.
Component(s)
Continuous Integration, Developer Tools