ProjectExplorer: Make sure kit removal is made persistent

At least one caller deregisters kits so late in the shutdown process
that the final KitManager::saveKits() has already run, so the removed kit
showed up again on the next start.

Fixes: QTCREATORBUG-31461
Change-Id: Ia9ad3f9ee9ba692b866f7105f944b308d7a22693
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/projectexplorer/kitmanager.cpp

@@ -651,6 +651,10 @@ void KitManager::deregisterKits(const QList<Kit *> kitList)
     for (auto it = removed.cbegin(); it != removed.cend(); ++it)
         emit instance()->kitRemoved(it->get());
     emit instance()->kitsChanged();
+
+    // FIXME: TargetSetupPage potentially deregisters kits on destruction, after the final
+    //        ICore::saveSettingsRequested() was emitted.
+    saveKits();
 }
 
 void KitManager::setDefaultKit(Kit *k)