use g4dn.xlarge

Author: mmcky

.github/workflows/ci.yml

@@ -2,7 +2,7 @@ name: Build Project [using jupyter-book]
 on: [pull_request]
 jobs:
   preview:
-    runs-on: "runs-on=${{ github.run_id }}/family=g4dn.2xlarge/image=quantecon_ubuntu2404/disk=large"
+    runs-on: "runs-on=${{ github.run_id }}/family=g4dn.xlarge/image=quantecon_ubuntu2404/disk=large"
     steps:
       - uses: actions/checkout@v4
         with: