refactor(dbus): Fix typo and remove unused thread instance

Corrected a typo in the `timeout` parameter name in `method_await_reset`
and removed an unused thread instance `th_sleep` from `dbus_helper.py`.
These changes improve code clarity and eliminate redundant components.

src/revpi_middleware/cli_commands/dbus_helper.py

@@ -96,7 +96,6 @@ def await_signal(
     detected_signal = False
     timeout = int(timeout)
     loop = GLib.MainLoop()
-    th_sleep = Thread()
 
     def th_timeout():
         sleep(timeout)