Update mcr.microsoft.com/dotnet/core/samples:aspnetapp to supported tag

Author: gholliday

articles/application-gateway/ingress-controller-add-health-probes.md

@@ -28,7 +28,7 @@ spec:
     spec:
       containers:
       - name: aspnetapp
-        image: mcr.microsoft.com/dotnet/core/samples:aspnetapp
+        image: mcr.microsoft.com/dotnet/samples:aspnetapp
         imagePullPolicy: IfNotPresent
         ports:
         - containerPort: 80

articles/application-gateway/ingress-controller-install-new.md

@@ -291,7 +291,7 @@ metadata:
     app: aspnetapp
 spec:
   containers:
-  - image: "mcr.microsoft.com/dotnet/core/samples:aspnetapp"
+  - image: "mcr.microsoft.com/dotnet/samples:aspnetapp"
     name: aspnetapp-image
     ports:
     - containerPort: 80

articles/application-gateway/ingress-controller-troubleshoot.md

@@ -37,7 +37,7 @@ metadata:
     app: test-agic-app
 spec:
   containers:
-  - image: "mcr.microsoft.com/dotnet/core/samples:aspnetapp"
+  - image: "mcr.microsoft.com/dotnet/samples:aspnetapp"
     name: aspnetapp-image
     ports:
     - containerPort: 80