Valgrind: Consolidate message production and consumption

Change-Id: I779f97a658b55f3c79111df1946b8d72863ce513
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/valgrind/valgrindengine.h

@@ -60,7 +60,6 @@ private:
     void handleProgressFinished();
     void runnerFinished();
 
-    void receiveProcessOutput(const QString &output, Utils::OutputFormat format);
     void receiveProcessError(const QString &message, QProcess::ProcessError error);
 
     QStringList genericToolArguments() const;