build(deps): bump actions/checkout from 3 to 4 (#1882)

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

.github/workflows/experimental_conformance.yaml

@@ -17,7 +17,7 @@ jobs:
       matrix:
         version: [ v1.26.6, v1.27.3, v1.28.0 ]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - uses: ./tools/github-actions/setup-deps
 
     # gateway api experimental conformance