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

@@ -15,7 +15,7 @@ jobs:
   rubocop:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: '3.4'
@@ -53,7 +53,7 @@ jobs:
       GRAPE_VERSION: ${{ matrix.entry.grape }}
     steps:
     - name: Check out branch
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with:

.github/workflows/danger.yml

@@ -6,7 +6,7 @@ jobs:
   danger:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v5
+    - uses: actions/checkout@v6
       with:
         fetch-depth: 100
     - name: Set up Ruby