Remove "Name Contains" query constraint from Diffusion for Repositories

Summary:
Ref T12819. Obsoleted by the Ferret engine "Query" field.

This is a compatibility break, I'll note it in the changelog.

Test Plan: Searched for repositories by name with "Query" instead of "Name Contains".

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12819

Differential Revision: https://secure.phabricator.com/D18588