Don't skip pickle check_frame_opcodes() (GH-15025)

This looks like the only place that proto 4 framing gets exercised
so leave it as part of the PGO task.

Author: nascheme

Lib/test/pickletester.py

@@ -2281,7 +2281,6 @@ def test_setitems_on_non_dicts(self):
     FRAME_SIZE_MIN = 4
     FRAME_SIZE_TARGET = 64 * 1024
 
-    @support.skip_if_pgo_task
     def check_frame_opcodes(self, pickled):
         """
         Check the arguments of FRAME opcodes in a protocol 4+ pickle.