Update label-prs.yml, fixing yml format (#9926)

https://eng.ms/docs/products/gitops/apps/examples/pr-triage

Author: DragosDanielBoia

.github/policies/label-prs.yml

@@ -5,8 +5,6 @@ resource: repository
 configuration:
   resourceManagementConfiguration:
     eventResponderTasks:
-    - description: Label main to live PRs
-    - triggerOnOwnActions: true
     - if:
       - payloadType: Pull_Request
       - isAction:
@@ -17,5 +15,7 @@ configuration:
       then:
       - addLabel:
           label: ':octocat: auto-merge'
+      description: Label main to live PRs
+      triggerOnOwnActions: true