Replace serial_asyncio with serial_asyncio_fast in unit tests

Co-authored-by: puddly <[email protected]>

Author: Copilot

tests/conftest.py

@@ -154,7 +154,7 @@ def passthrough_serial_conn(loop, protocol_factory, url, *args, **kwargs):
             return fut
 
         mocker.patch(
-            "serial_asyncio.create_serial_connection", new=passthrough_serial_conn
+            "serial_asyncio_fast.create_serial_connection", new=passthrough_serial_conn
         )
 
         # So we don't have to import it every time

tests/test_uart.py

@@ -1,7 +1,7 @@
 import asyncio
 
 import pytest
-from serial_asyncio import SerialTransport
+from serial_asyncio_fast import SerialTransport
 
 import zigpy_znp.types as t
 import zigpy_znp.config as conf
@@ -47,7 +47,7 @@ def create_serial_conn(loop, protocol_factory, url, *args, **kwargs):
 
         return fut
 
-    mocker.patch("serial_asyncio.create_serial_connection", new=create_serial_conn)
+    mocker.patch("serial_asyncio_fast.create_serial_connection", new=create_serial_conn)
 
     return device, serial_interface