Remove the extra done in gr-reporting_test

Change-Id: Id87f1bff9839dd4aabb4f33781f580235ed22487
(cherry picked from commit 6c2b0b0a44)

polygerrit-ui/app/elements/core/gr-reporting/gr-reporting_test.html

@@ -191,7 +191,6 @@ limitations under the License.
       assert.isTrue(element.reporter.calledOnce);
       assert.throws(() => {
         timer.end();
-        done();
       }, 'Timer for "foo-bar" already ended.');
     });