Removed unused import.

src/Renci.SshNet/Messages/Connection/GlobalRequestMessage.cs

@@ -1,6 +1,4 @@
-using Renci.SshNet.Abstractions;
-
-namespace Renci.SshNet.Messages.Connection
+namespace Renci.SshNet.Messages.Connection
 {
     /// <summary>
     /// Represents SSH_MSG_GLOBAL_REQUEST message.