Revert "Instruct robots to stop indexing zero.wikipedia.org and its subdomains."

Per adam's requset

This reverts commit d8641853563caa5029726dd9f521c653361dad3d

Change-Id: I64cddf784f4645265f3c4b5eca5a5a6fbe1a0ed5
Merge "Revert "Instruct robots to stop indexing zero.wikipedia.org and its subdomains.""