QmlProject: Use IRunConfiguration's changed() signal

... instead of directly accessing the owning runconfig.

The removes two uses of IRCAspect::runConfiguration()
which is meant to be removed soon.

Change-Id: Ia713864f2544e3c6741482b2663ee54fd2ee80e1
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

src/plugins/qmlprojectmanager/qmlprojectrunconfiguration.h

@@ -42,8 +42,6 @@ public:
     QmlProjectRunConfiguration(ProjectExplorer::Target *target, Core::Id id);
 
 private:
-    friend class MainQmlFileAspect;
-
     ProjectExplorer::Runnable runnable() const final;
     QString disabledReason() const final;
     ProjectExplorer::Abi abi() const final;