Fix inhibition rule for warning/critical severities

Change-Id: I3218b91a5047b9718ec5fbbf84615e49caf01a42
diff --git a/metadata/service/alertmanager/container.yml b/metadata/service/alertmanager/container.yml
index 161721b..f74687c 100644
--- a/metadata/service/alertmanager/container.yml
+++ b/metadata/service/alertmanager/container.yml
@@ -40,7 +40,7 @@
               severity: 'critical'
             target_match:
               severity: 'warning'
-            equal: ['alertname', 'region', 'service']
+            equal: ['region', 'service']
         receiver:
           HTTP-notification:
             enabled: true