Upgrade actions/checkout to v4

Signed-off-by: Yasumasa Suenaga <[email protected]>

Author: YaSuenag

.github/workflows/4.a.1-generate-webapi-client-java.yaml

@@ -65,7 +65,7 @@ jobs:
       contents: write
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Prepare
         run: mkdir -p ${{ env.DOCPATH }}
       - name: Download Javadoc