Use PEP 585 syntax wherever possible (#6717)

stdlib/smtplib.pyi

@@ -4,12 +4,12 @@ from email.message import Message as _Message
 from socket import socket
 from ssl import SSLContext
 from types import TracebackType
-from typing import Any, Dict, Pattern, Protocol, Sequence, Tuple, Type, Union, overload
+from typing import Any, Pattern, Protocol, Sequence, Type, Union, overload
 
-_Reply = Tuple[int, bytes]
-_SendErrs = Dict[str, _Reply]
+_Reply = tuple[int, bytes]
+_SendErrs = dict[str, _Reply]
 # Should match source_address for socket.create_connection
-_SourceAddress = Tuple[Union[bytearray, bytes, str], int]
+_SourceAddress = tuple[Union[bytearray, bytes, str], int]
 
 SMTP_PORT: int
 SMTP_SSL_PORT: int