Fix a false assertion

#assert was used when it should be assert_equal.

activerecord/test/cases/date_time_test.rb

@@ -55,7 +55,7 @@ def test_assign_in_local_timezone
     now = DateTime.now
     with_timezone_config default: :local do
       task = Task.new starting: now
-      assert now, task.starting
+      assert_equal now, task.starting
     end
   end
 end