Fix flaky timeout after boot slot switching test (#4113)

Add timeout to expect call when waiting for the OS reboot after
switching slots. While it never fails for me locally, it regularly
breaks tests in GHA.

(cherry picked from commit 98a7a55df6)

tests/smoke_test/test_os_update.py

@@ -3,7 +3,6 @@ import logging
 from time import sleep
 
 import pytest
-from labgrid.driver import ExecutionError
 
 _LOGGER = logging.getLogger(__name__)
 
@@ -86,7 +85,7 @@ def test_boot_other_slot(shell, shell_json, target):
 
     shell.run_check(f"ha os boot-slot other --no-progress || true")
 
-    shell.console.expect("Booting `Slot ")
+    shell.console.expect("Booting `Slot ", timeout=60)
 
     # reactivate ShellDriver to handle login again
     target.deactivate(shell)