Pick changes suggested by pyupgrade --py38-plus.

Other changes were ignored, on purpose.

src/websockets/sync/messages.py

@@ -53,8 +53,7 @@ def __init__(self) -> None:
         # value marking the end of the message, superseding message_complete.
 
         # Stream data from frames belonging to the same message.
-        # Remove quotes around type when dropping Python < 3.9.
-        self.chunks_queue: "queue.SimpleQueue[Data | None] | None" = None
+        self.chunks_queue: queue.SimpleQueue[Data | None] | None = None
 
         # This flag marks the end of the connection.
         self.closed = False

tests/legacy/test_client_server.py

@@ -65,7 +65,7 @@ async def default_handler(ws):
         await ws.wait_closed()
         await asyncio.sleep(2 * MS)
     else:
-        await ws.send((await ws.recv()))
+        await ws.send(await ws.recv())
 
 
 async def redirect_request(path, headers, test, status):

tests/legacy/utils.py

@@ -79,6 +79,6 @@ def assertDeprecationWarnings(self, recorded_warnings, expected_warnings):
         for recorded in recorded_warnings:
             self.assertEqual(type(recorded.message), DeprecationWarning)
         self.assertEqual(
-            set(str(recorded.message) for recorded in recorded_warnings),
+            {str(recorded.message) for recorded in recorded_warnings},
             set(expected_warnings),
         )