Bump actions/checkout from 2 to 4 (#224)

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>

.github/workflows/build.yaml

@@ -7,7 +7,7 @@ jobs:
         runs-on: ubuntu-latest
 
         steps:
-            - uses: actions/checkout@v2
+            - uses: actions/checkout@v4
             - uses: actions/setup-dotnet@v1
               with:
                   dotnet-version: "6.0.x"
@@ -41,7 +41,7 @@ jobs:
         # tag a release as v1.0.0....
         if: startsWith(github.ref, 'refs/tags/v')
         steps:
-            - uses: actions/checkout@v2
+            - uses: actions/checkout@v4
             - uses: actions/setup-dotnet@v1
               with:
                   dotnet-version: "6.0.x"