Add all the email __all__s (#7304)

stdlib/email/feedparser.pyi

@@ -2,6 +2,8 @@ from email.message import Message
 from email.policy import Policy
 from typing import Callable, Generic, TypeVar, overload
 
+__all__ = ["FeedParser", "BytesFeedParser"]
+
 _M = TypeVar("_M", bound=Message)
 
 class FeedParser(Generic[_M]):