refactor: remove redundant extractIdempotencyId from linear handler

The idempotency service already uses the Linear-Delivery header
(which Linear always sends) as the primary dedup key. The body-based
fallback was unnecessary defensive code.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: waleedlatif1

apps/sim/lib/webhooks/providers/linear.ts

@@ -293,13 +293,4 @@ export const linearHandler: WebhookProviderHandler = {
       })
     }
   },
-
-  extractIdempotencyId(body: unknown) {
-    const obj = body as Record<string, unknown>
-    const data = obj.data as Record<string, unknown> | undefined
-    if (obj.action && data?.id) {
-      return `${obj.action}:${data.id}`
-    }
-    return null
-  },
 }