fix(tradein): drop undefined _cancelled assign in cian-full-load cancel path

Review #929: _cancelled was removed earlier in the PR but a stray assignment
remained → NameError on every cooperative cancel (common exit path). Variable
unused; mark_done is called unconditionally next line.

tradein-mvp/backend/app/services/scrape_pipeline.py

@@ -1703,7 +1703,6 @@ async def run_cian_full_load(
     except RuntimeError as exc:
         # on_bucket кидает RuntimeError("cancelled") при cooperative cancel
         if str(exc) == "cancelled":
-            _cancelled = True
             logger.info(
                 "cian-full-load run_id=%d: cancelled — partial results unique=%d ins=%d upd=%d",
                 run_id,