Update actions/checkout action to v6 (#41)

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

Author: renovate[bot]

.github/workflows/style.yaml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
     - name: Checkout
-      uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd # v5.0.1
+      uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # v6.0.0
     - name: prek
       uses: glotzerlab/workflows/prek@894d9678188a02b06560fdeb2b9ba98d016cd371 # 0.10.0