cleanup references of python 2 & <3.11 (#35799)

* chore: cleanup of old python references

xmodule/capa/safe_exec/tests/test_safe_exec.py

@@ -306,13 +306,6 @@ class TestUpdateHash(unittest.TestCase):
         """
         d1 = {k: 1 for k in "abcdefghijklmnopqrstuvwxyz"}
         d2 = {k: 1 for k in "bcdefghijklmnopqrstuvwxyza"}
-        # TODO: remove the next lines once we are in python3.8
-        # since python3.8 dict preserve the order of insertion
-        # and therefore d2 and d1 keys are already in different order.
-        for i in range(10000):
-            d2[i] = 1
-        for i in range(10000):
-            del d2[i]
 
         # Check that our dicts are equal, but with different key order.
         assert d1 == d2