Remove dependency on python-argparse -- it isn't need with Python 2.7.

(imported from commit 388f6a5b7ff2b20364d22fad0d9e7d992791a18b)

puppet/zulip/manifests/postgres_common.pp

@@ -4,7 +4,6 @@ class zulip::postgres_common {
                         # tools for database setup
                         "pgtune",
                         # Python modules used in our monitoring/worker threads
-                        "python-argparse",
                         "python-gevent",
                         "python-tz",
                         "python-dateutil",