roles/postgres: Remove cache expiry time checks

After adding a new apt lists file, I think its a good idea to ignore
cache expiry times so that we can get packages from the new apt list.

Signed-off-by: James Oguya <oguyajames@gmail.com>

roles/postgresql/tasks/main.yml

@@ -8,7 +8,7 @@
   apt_key: url="https://www.postgresql.org/media/keys/ACCC4CF8.asc" state=present
 
 - name: Install postgresql
-  apt: name={{ item }} update_cache=yes state=present cache_valid_time=3600
+  apt: name={{ item }} update_cache=yes state=present
   with_items:
     - python-psycopg2
     - postgresql-{{ pg_version }}