Update auto-merge.yml

Author: gewarren

.github/policies/auto-merge.yml

@@ -16,6 +16,8 @@ configuration:
           label: ':octocat: auto-merge'
       - targetsBranch:
           branch: live
+      - isActivitySender:
+          user: microsoft-github-policy-service[bot]
       then:
       - enableAutoMerge:
           mergeMethod: Merge
@@ -26,4 +28,4 @@ configuration:
       - labelRemoved:
           label: ':octocat: auto-merge'
       then:
-      - disableAutoMerge
+      - disableAutoMerge