fix(scrapy): Close AsyncThread on scheduler open() failure (#820)

## Summary

- Close `AsyncThread` in the `except` block of `ApifyScheduler.open()` before re-raising, preventing a thread leak when `open_rq()` fails (Scrapy only calls `close()` after a successful `open()`).

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: vdusek

src/apify/scrapy/scheduler.py

@@ -61,6 +61,7 @@ async def open_rq() -> RequestQueue:
         try:
             self._rq = self._async_thread.run_coro(open_rq())
         except Exception:
+            self._async_thread.close()
             traceback.print_exc()
             raise