Minor spec change around UNAVAILABLE / RetryInfo

docs/specification.md

@@ -224,18 +224,12 @@ retryable and not-retryable:
   and cannot be deserialized or processed by the server. The client
   SHOULD maintain a counter of such dropped data.
 
-The server MUST indicate retryable errors using code
-[Unavailable](https://godoc.org/google.golang.org/grpc/codes) and MAY supply
-additional
-[details via status](https://godoc.org/google.golang.org/grpc/status#Status.WithDetails)
-using
-[RetryInfo](https://github.com/googleapis/googleapis/blob/6a8c7914d1b79bd832b5157a09a9332e8cbd16d4/google/rpc/error_details.proto#L40)
-containing 0 value of RetryDelay. Here is a sample Go code to illustrate:
+For retryable errors the server is recommended to use code
+[Unavailable](https://godoc.org/google.golang.org/grpc/codes).
 
 ```go
   // Do this on server side.
-  st, err := status.New(codes.Unavailable, "Server is unavailable").
-    WithDetails(&errdetails.RetryInfo{RetryDelay: &duration.Duration{Seconds: 0}})
+  st, err := status.New(codes.Unavailable, "Server is unavailable")
   if err != nil {
     log.Fatal(err)
   }