👷 Upgrade actions/checkout action to v6 (#12)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/makefile.yml

@@ -12,6 +12,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - name: checkout repo
-      uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5
+      uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6
     - name: test
       run: make test