Bump actions/checkout from 4 to 5

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build.yml

@@ -25,7 +25,7 @@ jobs:
     env:
       DOTNET_CLI_TELEMETRY_OPTOUT: 1
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v5

.github/workflows/sk2-ci.yml

@@ -17,7 +17,7 @@ jobs:
     env:
       DOTNET_CLI_TELEMETRY_OPTOUT: 1
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Setup .NET Core
         uses: actions/setup-dotnet@v5