Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...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.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
     - name: checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         submodules: true
 
@@ -75,7 +75,7 @@ jobs:
 
     steps:
     - name: checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         submodules: true
 

.github/workflows/release.yml

@@ -29,7 +29,7 @@ jobs:
 
     steps:
     - name: checkout
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
 
     - name: setup dotnet
       uses: actions/setup-dotnet@v5