Bump actions/checkout from 2 to 4 (#42)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...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>

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -29,7 +29,7 @@ jobs:
         runs-on: ${{matrix.os}}
 
         steps:
-          - uses: actions/checkout@v2
+          - uses: actions/checkout@v4
             with:
                 submodules: true
 

.github/workflows/docker.yaml

@@ -15,7 +15,7 @@ jobs:
     tests:
         runs-on: ubuntu-latest
         steps:
-          - uses: actions/checkout@v2
+          - uses: actions/checkout@v4
             with:
                 submodules: true