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

@@ -12,7 +12,7 @@ jobs:
     name: Lint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
@@ -26,7 +26,7 @@ jobs:
       matrix:
         ruby: ["2.7", "3.0", "3.1", "3.2", "3.3"]
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true

.github/workflows/publish.yml

@@ -16,7 +16,7 @@ jobs:
     needs: ci
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true
@@ -31,7 +31,7 @@ jobs:
     needs: ci
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           bundler-cache: true