chore(deps): update actions/checkout action to v6

Author: renovate[bot]

.github/workflows/check.yml

@@ -10,7 +10,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0
@@ -61,7 +61,7 @@ jobs:
             os: ubuntu-20.04
             extra-deps: "'virtualenv<20.22.0'"
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
       - uses: actions/setup-python@v5
         with:
           # >= 3.11 to ensure there's a recent one to run nox with

.github/workflows/release.yml

@@ -23,7 +23,7 @@ jobs:
     needs: release_please
     if: needs.release_please.outputs.release_created
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           ref: ${{ needs.release_please.outputs.sha }}
       - uses: actions/setup-python@v5