server: correct doc regarding unknown handlers and interceptors (#3195)

server.go

@@ -344,8 +344,8 @@ func StatsHandler(h stats.Handler) ServerOption {
 // unknown service handler. The provided method is a bidi-streaming RPC service
 // handler that will be invoked instead of returning the "unimplemented" gRPC
 // error whenever a request is received for an unregistered service or method.
-// The handling function has full access to the Context of the request and the
-// stream, and the invocation bypasses interceptors.
+// The handling function and stream interceptor (if set) have full access to
+// the ServerStream, including its Context.
 func UnknownServiceHandler(streamHandler StreamHandler) ServerOption {
 	return newFuncServerOption(func(o *serverOptions) {
 		o.unknownStreamDesc = &StreamDesc{