Remove unnecessary local connection

The "connection: local" option prevented us from running the playbook on
another host (e.g. an app server) which gets around security
restrictions on connecting to DB servers. Also, the option is totally
unnecessary. There's no reason this play couldn't run remotely.

playbooks/edx-east/create_db_and_users.yml

@@ -44,7 +44,6 @@
 
 - name: Create databases and users
   hosts: all
-  connection: local
   gather_facts: False
   tasks:
     # Install required library, currently this needs to be available