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/CI.yml

@@ -91,11 +91,11 @@ jobs:
         fi
         echo "filename=sc3-plugins-$VERSION-${{ matrix.name }}" >> $GITHUB_OUTPUT
     - name: checkout sc3-plugins
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         submodules: recursive
     - name: checkout supercollider
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         repository: supercollider/supercollider
         path: ${{ env.SC_SRC_PATH }}

.github/workflows/jekyll.yml

@@ -22,7 +22,7 @@ jobs:
       BUNDLE_FORCE_RUBY_PLATFORM: 'true' #  avoid platform mismatch for nokogiri
     steps:
     - name: checkout sc3-plugins
-      uses: actions/checkout@v5
+      uses: actions/checkout@v6
       with:
         submodules: recursive
     - name: setup ruby and build