Remove obsolete columns during update

This is a better version for https://gerrit.wikimedia.org/r/#/c/106464/

The bug:
An error occurred.
The error message received was: Exception Caught: Update not allowed on: tree_orig_user_text, rev_user_text, rev_edit_user_text

Change-Id: Iaf1693aade7c81bbd75fbe5f4a5f234c8861f032