Use latest container in CI

The domjudge/gitlabci:2.1 is not actively pushed anymore.

Author: vmcj

.github/workflows/codestyle.yml

@@ -13,7 +13,7 @@ jobs:
   syntax-job:
     runs-on: ubuntu-latest
     container:
-      image: domjudge/gitlabci:2.1
+      image: domjudge/gitlabci:24.04
     steps:
       - uses: actions/checkout@v4
       - name: Run the syntax checks

.github/workflows/runpipe.yml

@@ -15,7 +15,7 @@ jobs:
   runpipe:
     runs-on: ubuntu-latest
     container:
-      image: domjudge/gitlabci:2.1
+      image: domjudge/gitlabci:24.04
     steps:
       - uses: actions/checkout@v4
       - name: Create the configure file