rm-remote

• Usage: java gitlet.Main rm-remote [remote name]
• Description: Remove information associated with the given remote name. The idea here is that if you ever wanted to change a remote that you added, you would have to first remove it and then re-add it.
• Failure cases: If a remote with the given name does not exist, print the error message: A remote with that name does not exist.
• Dangerous?: No.