fix: GitHub Actions の checkout@v4 への更新

Author: nacchan99

.github/workflows/fetch_news.yml

@@ -12,7 +12,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Ruby
         uses: ruby/setup-ruby@v1