Revert "genericizing transformer" (#13063)

This reverts commit 4e65b1f14b.

common/lib/xmodule/xmodule/seq_module.py

@@ -117,14 +117,6 @@ class ProctoringFields(object):
         scope=Scope.settings,
     )
 
-    @property
-    def is_timed_exam(self):
-        """
-        Alias the permutation of above fields that corresponds to un-proctored timed exams
-        to the more clearly-named is_timed_exam
-        """
-        return not self.is_proctored_enabled and not self.is_practice_exam and self.is_time_limited
-
     @property
     def is_proctored_exam(self):
         """ Alias the is_proctored_enabled field to the more legible is_proctored_exam """