update minor api updates for github source. (#2100)

docs/eventing/samples/github-source/README.md

@@ -133,9 +133,10 @@ spec:
       name: githubsecret
       key: secretToken
   sink:
-    apiVersion: serving.knative.dev/v1
-    kind: Service
-    name: github-message-dumper
+    ref:
+      apiVersion: serving.knative.dev/v1
+      kind: Service
+      name: github-message-dumper
 ```
 
 Then, apply that yaml using `kubectl`:

docs/eventing/samples/github-source/github-source.yaml

@@ -15,8 +15,9 @@ spec:
       name: githubsecret
       key: secretToken
   sink:
-    apiVersion: serving.knative.dev/v1
-    kind: Service
-    name: github-message-dumper
+    ref:
+      apiVersion: serving.knative.dev/v1
+      kind: Service
+      name: github-message-dumper
 # To use GitHub Enterprise you would need to add an entry for your githubAPIURL similar to the example below
 # githubAPIURL: "https://github.mycompany.com/api/v3/"

docs/eventing/samples/github-source/service.yaml

@@ -7,4 +7,4 @@ spec:
   template:
     spec:
       containers:
-      - image: gcr.io/knative-releases/github.com/knative/eventing-sources/cmd/event_display
+      - image: gcr.io/knative-releases/github.com/knative/eventing-contrib/cmd/event_display