Update GitHub actions workflow for Java 21

Author: ERSUCC

.github/workflows/main.yml

@@ -11,7 +11,7 @@ jobs:
 
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v5
 
       - name: Set up Node
         uses: actions/setup-node@v3