Fix wrong type hints for SyndicationFeed methods

- The correct type is actually mentioned in django's documentation in
  docs/ref/contrib/syndication.txt.
- The previously defined type doesn't have methods like
  `addQuickElement`, which are used in Django's implementation of
  `add_root_elements`.

django-stubs/utils/feedgenerator.pyi

@@ -1,6 +1,7 @@
 import datetime
 from typing import Any
 from xml.sax import ContentHandler
+from xml.sax.saxutils import XMLGenerator
 
 from typing_extensions import TypeAlias
 
@@ -49,9 +50,13 @@ class SyndicationFeed:
     ) -> None: ...
     def num_items(self) -> int: ...
     def root_attributes(self) -> dict[Any, Any]: ...
-    def add_root_elements(self, handler: ContentHandler) -> None: ...
+    def add_root_elements(self, handler: XMLGenerator) -> None: ...
     def item_attributes(self, item: dict[str, Any]) -> dict[Any, Any]: ...
-    def add_item_elements(self, handler: ContentHandler, item: dict[str, Any]) -> None: ...
+    def add_item_elements(
+        self,
+        handler: XMLGenerator,
+        item: dict[str, Any],
+    ) -> None: ...
     def write(self, outfile: Any, encoding: Any) -> None: ...
     def writeString(self, encoding: str) -> str: ...
     def latest_post_date(self) -> datetime.datetime: ...