Delete authentication manager after destruction of the providers

The providers may still have threads running that use the authentication manager and their finished signal might trigger logic in the authentication manager.

src/core/qgsapplication.cpp

@@ -1177,8 +1177,6 @@ QgsAuthManager *QgsApplication::authManager()
 
 void QgsApplication::exitQgis()
 {
-  delete QgsApplication::authManager();
-
   //Ensure that all remaining deleteLater QObjects are actually deleted before we exit.
   //This isn't strictly necessary (since we're exiting anyway) but doing so prevents a lot of
   //LeakSanitiser noise which hides real issues
@@ -1191,6 +1189,8 @@ void QgsApplication::exitQgis()
 
   delete QgsProviderRegistry::instance();
 
+  delete QgsApplication::authManager();
+
   // invalidate coordinate cache while the PROJ context held by the thread-locale
   // QgsProjContextStore object is still alive. Otherwise if this later object
   // is destroyed before the static variables of the cache, we might use freed memory.