Revert "Version the tags xml file."

This reverts commit 20c947936be4f716286664ec76347d2824541903.

We cannot version the tags file since people will want to read their
original tags. We cannot distinguish between system tags and user
tags, since the user might have used system tags for their own resources.
And we cannot drop empty tags nilly-willy since the user might want
to create a tag, and re-use it later.