Fix pagination bug in dev/check_patch_prs.py (#20229)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: harupy <17039389+harupy@users.noreply.github.com>

Author: Copilot

dev/check_patch_prs.py

@@ -148,7 +148,7 @@ def fetch_patch_prs(version: str) -> dict[int, bool]:
         data = response.json()
         # Exclude closed PRs that are not merged
         pulls.extend(pr for pr in data["items"] if not is_closed(pr))
-        if len(data) < per_page:
+        if len(data["items"]) < per_page:
             break
         page += 1