Add AlmaLinux 8 & 9 support

Added AlmaLinux 8 and 9 to the supported operating systems in metadata.json.

These changes ensure that we start testing with AlmaLinux 8 and 9 instead
of CentOS 8 Stream. This update is part of our transition to better support
AlmaLinux in our Puppet modules.

See, for details: theforeman/foreman-infra#2087

metadata.json

@@ -52,6 +52,13 @@
         "18.04",
         "20.04"
       ]
+    },
+    {
+      "operatingsystem": "AlmaLinux",
+      "operatingsystemrelease": [
+        "8",
+        "9"
+      ]
     }
   ]
 }