fix: test flex updates ignoring 2.7

Author: iennae

appengine/flexible/hello_world/noxfile_config.py

@@ -22,7 +22,7 @@
 
 TEST_CONFIG_OVERRIDE = {
     # You can opt out from the test for specific Python versions.
-    "ignored_versions": ["2.7", "3.7"],
+    "ignored_versions": ["2.7", "3.7", "3.8"],
     # Old samples are opted out of enforcing Python type hints
     # All new samples should feature them
     "enforce_type_hints": True,