To bump off an accidental commit to origin, you'll have to sync your branch with the remote one.
Once that's done, we pop off the latest commit locally.
git reset HEAD^
The ^ means we're going back to the commit before "HEAD". Optionally you can use the option --hard to delete any changes made in that commit.
Now that we're back one commit, force it onto the remote master branch with +
git push origin +master
And that's it!