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](https://github.com/actions/checkout/compare/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] <support@github.com>

.github/workflows/windows-validation.yml

@@ -19,7 +19,7 @@ jobs:
         cache: [false, true]
         go: [1.20.1]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: 'Setup ${{ matrix.cache }}, cache: ${{ matrix.go }}'
         uses: ./
@@ -88,7 +88,7 @@ jobs:
       matrix:
         cache: [false, true]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: 'Setup default go, cache: ${{ matrix.cache }}'
         uses: ./
@@ -121,7 +121,7 @@ jobs:
         cache: [false]
         go: [1.20.1]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: 'Setup ${{ matrix.go }}, cache: ${{ matrix.cache }}'
         uses: ./