Remove typing_extensions dependency

Since Python 3.8 all used features from `typing_extensions` are also provided by the `typing` stdlib. Use those instead.

libmuscle/python/libmuscle/instance.py

@@ -3,9 +3,7 @@
 import logging
 import os
 import sys
-from typing import cast, Dict, List, Optional, Tuple, overload
-# TODO: import from typing module when dropping support for python 3.7
-from typing_extensions import Literal
+from typing import cast, Dict, List, Literal, Optional, Tuple, overload
 
 from ymmsl import (Identifier, Operator, SettingValue, Port, Reference,
                    Settings)

libmuscle/python/libmuscle/mcp/tcp_transport_server.py

@@ -1,8 +1,7 @@
 import socket
 import socketserver as ss
 import threading
-from typing import cast, List, Optional, Tuple
-from typing_extensions import Type
+from typing import cast, List, Optional, Tuple, Type
 
 import psutil
 

setup.py

@@ -59,7 +59,6 @@
         'psutil>=5.0.0',
         "numpy>=1.22",
         'qcg-pilotjob==0.13.1',
-        'typing_extensions>=4.4.0,<5',
         'ymmsl>=0.13.0,<0.14'          # Also in CI, update there as well
     ],
     extras_require={