Remove unnecessary files from the repo

[malleoz]

Since we are forking from Dolphin, obviously there are going to be some files which don't serve much purpose for our much more niche use-cases.

Do we need .mailmap? This seems to be a way to reference Dolphin developers for some purpose... Don't think that's necessary.
Do we need AndroidSetup.md? I would hope no one is trying to build this branch on Android devices to TAS...

The goal of this issue is to determine which files are unnecessary and ultimately remove or revise them.