Update actions/checkout action to v7

Author: renovate[bot]

.github/workflows/gametests.yml

@@ -54,7 +54,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: 'Checkout'
-        uses: actions/checkout@v6
+        uses: actions/checkout@v7
         with:
           submodules: true
       - name: 'Setup Java'