Explicitly update the repository URI index after making a URI edit

Summary:
Fixes T11936. After editing a repository URI, we were not correctly updating the URI index.

Any other edit to the repository would update the index, and this index is only really used by arc to figure out which repository a working copy belongs to, so that's how this evaded detection for this long. In particular, creating a repository would usually have an edit after any URI edits, to activate it, which would build the index correctly.

Test Plan:

• Added a new URI to a repository.
• Verified it was immediately reflected in the repository_uriindex table.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11936

Differential Revision: https://secure.phabricator.com/D16972