Bump actions/checkout from 3 to 4 (#397)

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]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/build-test-publish.yml

@@ -28,7 +28,7 @@ jobs:
         builder: ["buildpacks-20", "builder-classic-22", "builder-20", "builder-22", "salesforce-functions"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Install Pack CLI
         uses: buildpacks/github-actions/[email protected]
       - name: Create builder image
@@ -65,7 +65,7 @@ jobs:
             language: clojure
     steps:
       - name: Checkout getting started guide
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           ref: main
           repository: heroku/${{ matrix.language }}-getting-started.git
@@ -108,7 +108,7 @@ jobs:
         language: ["java", "javascript", "typescript"]
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
       - name: Install Pack CLI
         uses: buildpacks/github-actions/[email protected]
       - name: Restore Docker images from the cache