Debugger: Remove explicit GdbServerRunner's "Starting gdbserver ..."

Same (or similar, in case an explicit path is configured)  message
is triggered by the base class, no need for duplicated here.

Change-Id: I1a3e3c386674e98dc0ddd31f1156f7e8254a53c2
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/debugger/debuggerruncontrol.cpp

@@ -1078,9 +1078,6 @@ void GdbServerRunner::start()
     gdbserver.commandLineArguments = QtcProcess::joinArgs(args, OsTypeLinux);
 
     SimpleTargetRunner::setRunnable(gdbserver);
-
-    appendMessage(tr("Starting gdbserver..."), NormalMessageFormat);
-
     SimpleTargetRunner::start();
 }