Remove unused 'template' arg to _iter_loaders()

After last changes _iter_loaders makes no use of the 'template' argument.

flask/templating.py

@@ -75,7 +75,7 @@ class DispatchingJinjaLoader(BaseLoader):
             return tmplrv
         raise TemplateNotFound(template)
 
-    def _iter_loaders(self, template):
+    def _iter_loaders(self):
         loader = self.app.jinja_loader
         if loader is not None:
             yield self.app, loader