Fix GithubCopilotTask field name to match API response

Rename  to  to match the real GitHub Copilot API response. The test mock was already updated to use , but the model field name wasn't changed, causing Pydantic to silently drop the API value and leave the field as None.

Author: cursoragent

src/sentry/integrations/github_copilot/models.py

@@ -77,7 +77,7 @@ class GithubCopilotTask(BaseModel):
     session_count: int | None = None
     artifacts: list[GithubCopilotArtifact] | None = None
     archived_at: str | None = None
-    last_updated_at: str | None = None
+    updated_at: str | None = None
     created_at: str | None = None
     sessions: list[GithubCopilotSession] | None = None