Update an error message to make the error reporting look cleaner (#277)

Author: daxian-dbw

shell/agents/Microsoft.Azure.Agent/AzureAgent.cs

@@ -194,8 +194,7 @@ public async Task RefreshChatAsync(IShell shell, bool force)
             if (inner is CredentialUnavailableException)
             {
                 host.WriteErrorLine($"Failed to start a chat session: Access token not available.");
-                host.WriteErrorLine($"The '{Name}' agent depends on the Azure CLI credential to acquire access token. Please run 'az login' from a command-line shell to setup account.");
-                host.WriteErrorLine("Once you've successfully logged in, please run '/refresh' to start a new conversation");
+                host.WriteErrorLine($"The '{Name}' agent depends on the Azure CLI credential to acquire access token. Please run 'az login' from a command-line shell to setup account. Once you've successfully logged in, run '/refresh' to start a new conversation.");
                 return;
             }