Utils: Remove ChannelBuffer's QObject base

Not used anymore.

Change-Id: If149abbced43b0b476715073cafa5ad4fe918c24
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/libs/utils/qtcprocess.cpp

@@ -87,7 +87,7 @@ public:
 };
 
 // Data for one channel buffer (stderr/stdout)
-class ChannelBuffer : public QObject
+class ChannelBuffer
 {
 public:
     void clearForRun();