Cleanup needless robots.txt rules for wikitech

- Removed a lot of wikipedia specific rules that make no sense here
- Removed exception for MobileFrontend since it is not installed
- Removed some commented out rules
- Removed special pages that were listed in multiple languages
- Haven't removed specific bots that were listed. Unsure how to
  verify if they are still an issue.

Change-Id: I6149549679be1dc2056ba6db5de27df559c02b21