Delete py2 checks

No script can run on py2 (due to print syntax change), so those
checks are useless (will never be printed).

Change-Id: I9cc7bc8b2665dd09cc7f8939ba255956f96af88a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5262958
Commit-Queue: Josip Sokcevic <sokcevic@chromium.org>
Reviewed-by: Gavin Mak <gavinmak@google.com>

my_activity.py

@@ -53,10 +53,6 @@ import fix_encoding
 import gclient_utils
 import gerrit_util
 
-if sys.version_info.major == 2:
-    logging.critical(
-        'Python 2 is not supported. Run my_activity.py using vpython3.')
-
 try:
     import dateutil  # pylint: disable=import-error
     import dateutil.parser