Fix up rbintegrations tests that use old trophies API.
Review Request #10921 — Created Feb. 26, 2020 and submitted — Latest diff uploaded
Review Board 3.0 changed the trophies registry to actually use a real
registry instead of ad-hoc register and unregister methods, and
deprecated the old API. This was then removed entirely in Review Board
4. This change updates the unit tests to use that new API.
Ran rbintegrations tests.