[5.1.x] Refs #29850 -- Removed obsolete test_window_frame_raise_not_supported_error.

This NotSupportedError was removed in 6375cee
because it will never be reached due to the same exception raised by
Window.as_sql().

Backport of 94436de from main.

Author: timgraham

tests/backends/base/test_operations.py

@@ -174,12 +174,6 @@ class DatabaseOperationTests(TestCase):
     def setUp(self):
         self.ops = BaseDatabaseOperations(connection=connection)
 
-    @skipIfDBFeature("supports_over_clause")
-    def test_window_frame_raise_not_supported_error(self):
-        msg = "This backend does not support window expressions."
-        with self.assertRaisesMessage(NotSupportedError, msg):
-            self.ops.window_frame_rows_start_end()
-
     @skipIfDBFeature("can_distinct_on_fields")
     def test_distinct_on_fields(self):
         msg = "DISTINCT ON fields is not supported by this database backend"