[CI] M1 - Mac Big Sur (11.5): Agent pool update (#13095)

tools/devops/automation/build-pipeline.yml

@@ -100,11 +100,14 @@ parameters:
     {
       stageName: 'mac_11_5_m1',
       displayName: 'M1 - Mac Big Sur (11.5)',
-      macPool: 'VSEng-VSMac-Xamarin-Shared-Trusted',
+      macPool: 'VSEng-VSMac-Xamarin-Shared',
       statusContext: 'M1 - Mac Big Sur (11.5)',
       demands: [
         "Agent.OS -equals Darwin",
-        "macOS.Architecture -equals arm64"
+        "macOS.Name -equals BigSur",
+        "macOS.Architecture -equals arm64",
+        "Agent.HasDevices -equals False",
+        "Agent.IsPaired -equals False"
       ]
     }]