fix test

Author: isoos

app/test/admin/moderation_case_resolve_test.dart

@@ -91,11 +91,12 @@ void main() {
       'SHOUT Deleting object from public bucket: "packages/oxygen-1.2.0.tar.gz".',
       'SHOUT Deleting object from public bucket: "packages/oxygen-2.0.0-dev.tar.gz".',
     ], fn: () async {
+      final starTime = clock.now();
       final mc = await _prepare(apply: true);
 
       // cleanup doesn't remove case prematurely
       await _verifyCaseExistence(mc.caseId, true);
-      await adminBackend.deleteModerationCases(before: clock.now().toUtc());
+      await adminBackend.deleteModerationCases(before: starTime);
       await _verifyCaseExistence(mc.caseId, true);
 
       // close case