CMake: Remove unnecessary members from CMakeTargets

Change-Id: I6428496f4eab0d42f44525477c716f74714f8824
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cmakeprojectmanager/cmakeproject.h

@@ -64,7 +64,6 @@ public:
     QString workingDirectory;
     QString sourceDirectory;
     QString makeCommand;
-    QString makeCleanCommand;
 
     // code model
     QStringList includeFiles;