chore(eco): remove halt for unfurlable link

[cathteng]

This is extremely noisy and doesn't add any value

[sentry]

Bug: Removing lifecycle.record_halt() for unfurlable links causes IntegrationEventLifecycle to incorrectly record them as SUCCESS instead of HALTED.
_{Severity: CRITICAL | Confidence: High}

🔍 Detailed Analysis

When a link cannot be unfurled (i.e., link_type is None or args is None), the removal of lifecycle.record_halt() prevents explicit state setting. Due to the IntegrationEventLifecycle context's default assume_success=True, the event is incorrectly recorded as SUCCESS upon context exit instead of HALTED. This misrepresents the actual success rate of Slack integration's link unfurling, leading to corrupted metrics and misleading operational data.

💡 Suggested Fix

Either restore lifecycle.record_halt() and implement sampling/filtering to reduce noise, or initialize the IntegrationEventLifecycle context with assume_success=False to ensure unhandled exits default to HALTED.

🤖 Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: src/sentry/integrations/slack/webhooks/event.py#L189-L190

Potential issue: When a link cannot be unfurled (i.e., `link_type is None or args is
None`), the removal of `lifecycle.record_halt()` prevents explicit state setting. Due to
the `IntegrationEventLifecycle` context's default `assume_success=True`, the event is
incorrectly recorded as `SUCCESS` upon context exit instead of `HALTED`. This
misrepresents the actual success rate of Slack integration's link unfurling, leading to
corrupted metrics and misleading operational data.

_{Did we get this right? 👍 / 👎 to inform future reviews.
Reference ID: 4620354}

[cathteng]

that's correct :)