fix(canvas): drop duplicate model key after rebase

Rebase merged main's pinned DEFAULT_GATEWAY_MODEL with the branch's
gateway-resolved model into one createTask literal; the resolved
model wins.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: adamleithp

packages/ui/src/features/canvas/hooks/useGenerateContext.ts

@@ -1,4 +1,3 @@
-import { DEFAULT_GATEWAY_MODEL } from "@posthog/agent/gateway-models";
 import type { PostHogAPIClient } from "@posthog/api-client/posthog-client";
 import {
   REPORT_MODEL_RESOLVER,
@@ -140,11 +139,6 @@ export function useGenerateContext() {
             // before publishing, so the user co-designs CONTEXT.md.
             executionMode: "plan",
             allowNoRepo: true,
-            // A cloud run pairs a runtime adapter with a model, and the API
-            // rejects one without the other. Since this flow lets the agent pick
-            // its repo at runtime, it never surfaces a model picker, so pin the
-            // default gateway model here to match the adapter the saga defaults to.
-            model: DEFAULT_GATEWAY_MODEL,
           },
           (output) => invalidateTasks(output.task),
         );