roles/common: Relax SSH rate limit in firewalld

Now that I'm blocking ~10,000 malicious IPs from AbuseIPDB I feel
more comfortable using a more relaxed rate limit for SSH. A limit
of 12 per minute is about one every five seconds.

roles/common/templates/public.xml.j2

@@ -8,7 +8,7 @@
         <source address="0.0.0.0/0"/>
         <port protocol="tcp" port="22"/>
         <accept>
-            <limit value="5/m"/>
+            <limit value="12/m"/>
         </accept>
     </rule>
 
@@ -17,7 +17,7 @@
         <source address="::/0"/>
         <port protocol="tcp" port="22"/>
         <accept>
-            <limit value="5/m"/>
+            <limit value="12/m"/>
         </accept>
     </rule>