Add all the email __all__s (#7304)

stdlib/email/encoders.pyi

@@ -1,5 +1,7 @@
 from email.message import Message
 
+__all__ = ["encode_7or8bit", "encode_base64", "encode_noop", "encode_quopri"]
+
 def encode_base64(msg: Message) -> None: ...
 def encode_quopri(msg: Message) -> None: ...
 def encode_7or8bit(msg: Message) -> None: ...