refactor: websockets serve import

Newest websockets library doesn't work anymore with:
`from websockets.server import serve`

Author: zehnm

ucapi/api.py

@@ -19,8 +19,8 @@
 # workaround for pylint error: E0611: No name 'ConnectionClosedOK' in module 'websockets' (no-name-in-module)  # noqa
 from websockets.exceptions import ConnectionClosedOK
 
-# workaround for pylint error: E1101: Module 'websockets' has no 'serve' member (no-member)  # noqa
-from websockets.server import serve
+# Note: websockets ~v15 doesn't have websockets.server anymore
+from websockets import serve
 from zeroconf import IPVersion
 from zeroconf.asyncio import AsyncServiceInfo, AsyncZeroconf