ICore: Remove unused methods

Some didn't even have implementations anymore

Change-Id: I376cb12006c9b3ec8f6b2a75c38275cd92d2bbf6
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/coreplugin/icore.cpp

@@ -321,8 +321,6 @@ ICore::ICore(MainWindow *mainwindow)
         emit coreAboutToClose();
         QCoreApplication::exit(failedTests);
     });
-    connect(m_mainwindow, &MainWindow::newItemDialogRunningChanged,
-            this, &ICore::newItemDialogRunningChanged);
 }
 
 ICore::~ICore()