update runner name

Author: mmcky

.github/workflows/ci.yml

@@ -2,7 +2,7 @@ name: Build Project [using jupyter-book]
 on: [pull_request]
 jobs:
   preview:
-    runs-on: ubuntu-latest-gpu
+    runs-on: quantecon-gpu-runner
     container:
       image: ghcr.io/quantecon/lecture-python-container:cuda-12.5.0-anaconda-2024-06-py311
       options: --gpus all