test(telegram): run the ingress admission case for the full stall threshold

Fold of gate finding (2c Medium regression): raising _INGRESS_DISPATCH_STALL_HEARTBEATS to 4
left the `ingress` row of test_only_pre_handoff_failure_reopens_admission looping 3 heartbeats,
which can never reach the threshold, so its "no healthy-but-deaf report" assertion was disarmed.
Loop the threshold itself so the leg tracks future bumps. Verified: with update_admission's
dispatch counting removed, the heartbeat leg now fails (it passed with range(3)).

tests/plugins/test_telegram_update_admission.py

@@ -20,6 +20,7 @@ from telegram.request import BaseRequest
 
 from gateway.config import PlatformConfig
 from gateway.platforms.event import MessageType
+from plugins.platforms.telegram import adapter as tg_adapter
 from plugins.platforms.telegram.adapter import TelegramAdapter
 
 
@@ -508,7 +509,7 @@ async def test_only_pre_handoff_failure_reopens_admission(monkeypatch, tmp_path,
                 await app.process_update(update(app.bot))
             assert not adapter._seen_update_ids and not adapter._inflight_update_ids
             assert adapter._updates_dispatched_total == 2
-            for _ in range(3):
+            for _ in range(tg_adapter._INGRESS_DISPATCH_STALL_HEARTBEATS):
                 adapter._check_ingress_dispatch_stall()
             assert not any("healthy but deaf" in record.message for record in caplog.records)
             return