Use matchers for inhibit rules examples (#4131)

* This file is used when building binaries, while using deprecated
  {source,target}_match.
* Backport of commit 0ed31c3311
  from beorn7 <beorn@grafana.com>

Signed-off-by: LCT <lct@lct.pw>

examples/ha/alertmanager.yml

@@ -9,8 +9,11 @@ receivers:
     webhook_configs:
       - url: 'http://127.0.0.1:5001/'
 inhibit_rules:
-  - source_match:
-      severity: 'critical'
-    target_match:
-      severity: 'warning'
-    equal: ['alertname', 'dev', 'instance']
+  - source_matchers: [severity="critical"]
+    target_matchers: [severity="warning"]
+    # Apply inhibition if the alertname is the same.
+    # CAUTION:
+    #   If all label names listed in `equal` are missing
+    #   from both the source and target alerts,
+    #   the inhibition rule will apply!
+    equal: [alertname, dev, instance]