Update actions/checkout action to v7 (#143)

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

Author: renovate[bot]

.github/workflows/start.yaml

@@ -33,7 +33,7 @@ jobs:
       active: ${{ steps.start.outputs.active }}
     steps:
     - name: Checkout
-      uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+      uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
       with:
         repository: glotzerlab/jetstream2-admin
         ref: ${{ inputs.ref }}

.github/workflows/style.yaml

@@ -18,7 +18,7 @@ jobs:
     runs-on: ubuntu-24.04
     steps:
     - name: Checkout
-      uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+      uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
     - name: prek
       uses: glotzerlab/workflows/prek@00c67cb577c36bdc2570845fc62d1a30e3383012 # 0.14.0