pbio/sys/program_stop: Drop hack to stop Bluetooth.

We have an old hack that shuts down the bluetooth process. When starting a new task after that in a cleanup routine such as added in 04fd2e7, the hub will never finish the task, which prevents the user program from stopping.

We have several proper fixes in place now, and we are about to merge some updates that will make all Bluetooth task objects static, so we should remove this hack.

Fixes pybricks/support#1438

lib/pbio/sys/program_stop.c

@@ -32,12 +32,6 @@ static bool stop_button_pressed;
  */
 void pbsys_program_stop(bool force_stop) {
     if (pbsys_status_test(PBIO_PYBRICKS_STATUS_USER_PROGRAM_RUNNING)) {
-        if (force_stop) {
-            // HACK: Bluetooth drivers have issues with pending tasks not being
-            // cancellable, so this should force them to be canceled and avoid
-            // undefined behavior due to use after free.
-            pbdrv_bluetooth_power_on(false);
-        }
         pbsys_main_stop_program(force_stop);
     }
 }