update Hugo version to 0.87.0 in GitHub Actions workflow

Author: shunk031

.github/workflows/gh-pages.yml

@@ -21,7 +21,7 @@ jobs:
       - name: Setup Hugo
         uses: peaceiris/actions-hugo@v3
         with:
-          hugo-version: "latest"
+          hugo-version: "0.87.0"
           extended: true
 
       - name: Build