Remove the old removal logics from Torbutton

torbutton@2dfa0e0c introduced some logic to remove old files ($profile/cookies|protected-*.json) that aren't used anymore.

However, after the 12.0 watershed, we don't need it for sure anymore.

Also, there is a function to mess with preferences that we don't need anymore.

So, as part of the great torbutton cleanup, remove all of this.