test(slack): address review nits on the subtype allowlist

Drop the unreachable handle_message assertion in the drop tests
(_prefilter_inbound never calls it) and state the deliberate
file_comment drop decision in the allowlist comment.

plugins/platforms/slack/adapter.py

@@ -4313,6 +4313,8 @@ class SlackAdapter(BasePlatformAdapter):
         # ``me_message`` passes: ``/me`` is a person speaking.
         # ``bot_message`` already passed allow_bots above; document_mention is an
         # explicit app mention from a Slack canvas, not a lifecycle notification.
+        # ``file_comment`` stays in the drop set deliberately (triage decision on
+        # #110778): a comment left on a file is not the owner talking to the bot.
         subtype = event.get("subtype")
         if subtype not in (
             None, "", "file_share", "thread_broadcast", "me_message",

tests/gateway/test_slack.py

@@ -6093,7 +6093,6 @@ class TestNonConversationalSubtypeAllowlist:
     )
     async def test_housekeeping_subtypes_are_dropped(self, adapter, subtype):
         assert await adapter._prefilter_inbound(self._event(subtype), None) is None
-        adapter.handle_message.assert_not_awaited()
 
     @pytest.mark.asyncio
     @pytest.mark.parametrize(