On the ip-validator
branch, you'd do git rebase -i HEAD~2
- this will start an interactive rebase back two commits on that branch.
At this point, you'll get an editor open with options seen here: https://help.github.com/articles/interactive-rebase
Simply put, to remove that commit, just delete the commit line in the editor, save that editor file, and git will create a new commit without the commit you removed.