Remove collaborator

I created a local repository and did a git commit before setting the and in the git settings. After making the commit I defined the and and uploaded the commit to github, and there was the commit in the name of another user I don’t know.
Screenshot from 2021-10-06 00-49-31
(The top user is mine, the bottom one is the unknown.)
I did a git rebase to change the author of the first commit, but it still shows this user as a contributor. I would like to know how to remove it.