remove examples

Signed-off-by: Billy Zha <jinzha1@microsoft.com>

cmd/oras/root/attach.go

@@ -54,10 +54,6 @@ func attachCmd() *cobra.Command {
 Example - Attach file 'hi.txt' with type 'doc/example' to manifest 'hello:v1' in registry 'localhost:5000':
   oras attach --artifact-type doc/example localhost:5000/hello:v1 hi.txt
 
-Example - Attach file "hi.txt" with specific media type when building the manifest:
-  oras attach --artifact-type doc/example --image-spec v1.1-image localhost:5000/hello:v1 hi.txt    # OCI image
-  oras attach --artifact-type doc/example --image-spec v1.1-artifact localhost:5000/hello:v1 hi.txt # OCI artifact
-
 Example - Attach file "hi.txt" using a specific method for the Referrers API:
   oras attach --artifact-type doc/example --distribution-spec v1.1-referrers-api localhost:5000/hello:v1 hi.txt # via API
   oras attach --artifact-type doc/example --distribution-spec v1.1-referrers-tag localhost:5000/hello:v1 hi.txt # via tag scheme

cmd/oras/root/push.go

@@ -71,10 +71,6 @@ Example - Push file "hi.txt" with config type "application/vnd.me.config":
 Example - Push file "hi.txt" with the custom manifest config "config.json" of the custom media type "application/vnd.me.config":
   oras push --config config.json:application/vnd.me.config localhost:5000/hello:v1 hi.txt
 
-Example - Push file "hi.txt" with specific media type when building the manifest:
-  oras push --image-spec v1.1-image localhost:5000/hello:v1 hi.txt    # OCI image
-  oras push --image-spec v1.1-artifact localhost:5000/hello:v1 hi.txt # OCI artifact
-
 Example - Push file to the insecure registry:
   oras push --insecure localhost:5000/hello:v1 hi.txt