Add import to gr-registration-dialog_test

Otherwise you cannot run the test on its own.

Change-Id: I18b7818b7d5a26dd596f618ecc8488874442ec17
(cherry picked from commit 1f39c5f89326fdae0c89ad2ca1a64ceb1836de24)
diff --git a/polygerrit-ui/app/elements/settings/gr-registration-dialog/gr-registration-dialog_test.ts b/polygerrit-ui/app/elements/settings/gr-registration-dialog/gr-registration-dialog_test.ts
index 07a2e51..3c09d5e 100644
--- a/polygerrit-ui/app/elements/settings/gr-registration-dialog/gr-registration-dialog_test.ts
+++ b/polygerrit-ui/app/elements/settings/gr-registration-dialog/gr-registration-dialog_test.ts
@@ -15,6 +15,7 @@
  * limitations under the License.
  */
 import '../../../test/common-test-setup-karma';
+import './gr-registration-dialog';
 import {GrRegistrationDialog} from './gr-registration-dialog';
 import {queryAndAssert, stubRestApi} from '../../../test/test-utils';
 import {AccountDetailInfo, Timestamp} from '../../../types/common';