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] <support@github.com>

Author: dependabot[bot]

.github/workflows/benchmark.yml

@@ -16,7 +16,7 @@ jobs:
           - ubuntu-latest
     runs-on: ${{ matrix.runs-on }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby-version }}

.github/workflows/release.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - name: Extract release note
         run: |
           ruby \
@@ -37,7 +37,7 @@ jobs:
       id-token: write
     environment: release
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ruby

.github/workflows/test.yml

@@ -27,7 +27,7 @@ jobs:
         #   - runs-on: ubuntu-latest
         #     ruby-version: truffleruby
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby-version }}
@@ -39,7 +39,7 @@ jobs:
     name: frozen-string-literal
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ruby
@@ -66,7 +66,7 @@ jobs:
           - windows-latest
         ruby-version: ${{ fromJson(needs.ruby-versions-gems.outputs.versions) }}
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ${{ matrix.ruby-version }}
@@ -95,7 +95,7 @@ jobs:
     name: "Document"
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ruby/setup-ruby@v1
         with:
           ruby-version: ruby
@@ -105,7 +105,7 @@ jobs:
       - name: Build document
         run: |
           bundle exec rake warning:error rdoc
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         if: |
           github.event_name == 'push'
         with: