Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/build.yml

@@ -19,7 +19,7 @@ jobs:
     steps:
       - id: setup-env
         uses: cisagov/setup-env-github-action@develop
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - id: setup-python
         uses: actions/setup-python@v4
         with:

.github/workflows/sync-labels.yml

@@ -19,7 +19,7 @@ jobs:
       issues: write
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - name: Sync repository labels
         if: success()
         uses: crazy-max/ghaction-github-labeler@v4