Only build nginx-errors for linux/amd64 (#7625)

* Fix wrong image location used in nginx-errors example config

* Only build nginx-errors for linux/amd64

docs/examples/customization/custom-errors/custom-default-backend.yaml

@@ -36,7 +36,7 @@ spec:
     spec:
       containers:
       - name: nginx-error-server
-        image: gcr.io/k8s-staging-ingress-nginx/nginx-errors:0.48.1
+        image: k8s.gcr.io/ingress-nginx/nginx-errors:0.48.1
         ports:
         - containerPort: 8080
         # Setting the environment variable DEBUG we can see the headers sent 

images/custom-error-pages/Makefile

@@ -29,7 +29,7 @@ IMAGE = $(REGISTRY)/nginx-errors
 export DOCKER_CLI_EXPERIMENTAL=enabled
 
 # build with buildx
-PLATFORMS?=linux/amd64,linux/arm,linux/arm64
+PLATFORMS?=linux/amd64
 OUTPUT=
 PROGRESS=plain