Merge pull request Cysharp#480 from Cysharp/hotfix/ClarifyMessageOnFa…

…iledToNegociate

Clarify the message when it fails to negotiate with the server

src/MagicOnion.Client/StreamingHubClientBase.cs

@@ -103,7 +103,7 @@ public async Task __ConnectAndSubscribeAsync(TReceiver receiver, CancellationTok
                 await firstMoveNextTask.ConfigureAwait(false);
 
                 // NOTE: C-core: If the execution reaches here, Connect method returns without any error (StatusCode = OK). but MessageVersion isn't provided from the server.
-                throw new RpcException(new Status(StatusCode.Internal, $"The message version of StreamingHub is not provided from the server."));
+                throw new RpcException(new Status(StatusCode.Internal, $"The request completed successfully (StatusCode = OK), but the StreamingHub client has failed to negotiate with the server."));
             }
 
             this.subscription = StartSubscribe(syncContext, firstMoveNextTask);