Bump actions/checkout from 4 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/ci-build.yml

@@ -16,7 +16,7 @@ jobs:
       webproject-path: './src/GitHubCostVisualizer.Web/GitHubCostVisualizer.Web.csproj'
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0
 

.github/workflows/release-build.yml

@@ -14,7 +14,7 @@ jobs:
       webproject-path: './src/GitHubCostVisualizer.Web/GitHubCostVisualizer.Web.csproj'
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 0