Utils: Don't expose Utils::defaultExitCodeInterpreter

Instead, make its behavior implicit if none is given.

Change-Id: I3c1a054751a0afe22d0f40a2fed6dd00b5aef205
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cvs/cvsplugin.cpp

@@ -208,7 +208,7 @@ public:
                                               : SynchronousProcessResponse::Finished;
             };
         }
-        return Utils::defaultExitCodeInterpreter;
+        return {};
     }
 
     Utils::Id vcsEditorKind(VcsCommandTag cmd) const override