ci: use checkout@v4

Author: krichprollsch

.github/workflows/zig-test.yml

@@ -57,7 +57,7 @@ jobs:
     runs-on: ubuntu-24.04
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           submodules: true