QProcess: remove unused member

Change-Id: I448a32b8ba11426c70d49f7f492b73e7799cc257
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qprocess.cpp

@@ -865,7 +865,6 @@ void QProcessPrivate::cleanup()
 
 #endif
     pid = 0;
-    sequenceNumber = 0;
 
     if (stdoutChannel.notifier) {
         delete stdoutChannel.notifier;

src/corelib/io/qprocess_p.h

@@ -308,7 +308,6 @@ public:
 #else
     qint64 pid = 0;
 #endif
-    int sequenceNumber;
 
     bool dying = false;
     bool emittedReadyRead = false;