Changes skip test for bigip user (#24799)

All of the F5 Ansible modules will come to require the same major
dependencies over time. This mentions that.

test/units/modules/network/f5/test_bigip_user.py

@@ -25,7 +25,7 @@ import pytest
 
 if sys.version_info < (2, 7):
     from nose.plugins.skip import SkipTest
-    raise SkipTest("test_bigip_user.py requires Python >= 2.7")
+    raise SkipTest("F5 Ansible modules require Python >= 2.7")
 
 import os
 import json