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] <support@github.com>

.github/workflows/citest.yml

@@ -19,7 +19,7 @@ jobs:
       uses: actions/setup-go@v4
       with:
         go-version: ${{ matrix.go-version }}
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@v4
     - run: |
         sudo sh -c 'echo "deb [signed-by=/etc/apt/trusted.gpg.d/naemon.asc] http://download.opensuse.org/repositories/home:/naemon/xUbuntu_$(lsb_release -rs)/ ./" >> /etc/apt/sources.list.d/naemon-stable.list'
         sudo curl -s -o /etc/apt/trusted.gpg.d/naemon.asc "https://build.opensuse.org/projects/home:naemon/signing_keys/download?kind=gpg"