r/squid: Let squid initialize cache dirs

The `squid.service` systemd unit now correctly initializes the
configured cache directories, so we do not need to do it explicitly
before starting the server.

roles/squid/tasks/main.yml

@@ -15,7 +15,7 @@
     state: directory
   loop: '{{ squid_cache_dir|d([]) }}'
   notify:
-  - initialize squid cache directories
+  - restart squid
 
 - name: ensure squid is configured
   template:
@@ -26,7 +26,6 @@
     group=squid
     setype=squid_conf_t
   notify:
-  - initialize squid cache directories
   - reload squid
 
 - name: ensure squid systemd unit drop-in directory exists