Move double entry later in update_5()

In the user_relationships_update_5() function, the 'INSERT INTO ...' statement happens early in the function, before several table manipulation statements. I recommend moving the 'INSERT INTO ...' to the end of the list of queries.

As a point of reference, we ran tests with ~500,000 relationships (before the update). Executing the SQL statements associated with update_5, in the original order, took about 92 seconds. When we moved the INSERT to the end, they took only 58 seconds. That's a noticeable improvement, and every little bit helps when your site is down for maintenance.