Removes the 'extensions' directory from pyrightconfig.json and fixes … (#26512)

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

api/pyrightconfig.json

@@ -5,7 +5,6 @@
     ".venv",
     "migrations/",
     "core/rag",
-    "extensions",
     "core/app/app_config/easy_ui_based_app/dataset"
   ],
   "typeCheckingMode": "strict",