pre-upload: enable Python 2 deprecation warning

We don't support Python 2 at all.  Warn anyone still using that
version so they need to migrate by end of year.

Bug: None
Test: `repo-1 upload` using python2 emits a warning
Change-Id: I8d7265399273086a7ac4151039e699277841be2e
diff --git a/pre-upload.py b/pre-upload.py
index d7c12aa..0d0afb6 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -38,7 +38,7 @@
     # We don't actually test <Python-3.6.  Hope for the best!
     print('repohooks: error: Python-3.4+ is required', file=sys.stderr)
     sys.exit(1)
-elif sys.version_info.major == 3 and sys.version_info < (3, 6):
+elif sys.version_info < (3, 6):
     # We want to get people off of old versions of Python.
     print('repohooks: warning: Python-3.6+ is going to be required; '
           'please upgrade soon to maintain support.', file=sys.stderr)