Improve documentation and examples [ci skip]

docs/examples/auth/client-certs/nginx-tls-auth.yaml

@@ -7,7 +7,6 @@ metadata:
     ingress.kubernetes.io/auth-tls-verify-depth: "3"
     ingress.kubernetes.io/auth-tls-verify-client: "on"
     auth-tls-error-page: "http://www.mysite.com/error-cert.html"
-    kubernetes.io/ingress.class: "nginx"
   name: nginx-test
   namespace: default
 spec:

docs/examples/customization/configuration-snippets/ingress.yaml

@@ -3,7 +3,6 @@ kind: Ingress
 metadata:
   name: nginx-configuration-snippet
   annotations:
-    kubernetes.io/ingress.class: "nginx"
     ingress.kubernetes.io/configuration-snippet: |
       more_set_headers "Request-Id: $request_id";
 

docs/examples/static-ip/nginx-ingress.yaml

@@ -2,8 +2,6 @@ apiVersion: extensions/v1beta1
 kind: Ingress
 metadata:
   name: ingress-nginx
-  annotations:
-    kubernetes.io/ingress.class: "nginx"
 spec:
   tls:
   # This assumes tls-secret exists.

docs/examples/tls-termination/ingress.yaml

@@ -2,8 +2,6 @@ apiVersion: extensions/v1beta1
 kind: Ingress
 metadata:
   name: nginx-test
-  annotations:
-    kubernetes.io/ingress.class: "nginx"
 spec:
   tls:
   # This assumes tls-secret exists.