Bump actions/checkout from 5 to 6 (#29)

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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/deploy-assets-to-svn.yml

@@ -8,7 +8,7 @@ jobs:
     name: Push assets and readme to trunk
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: WordPress.org plugin asset/readme update
         uses: 10up/action-wordpress-plugin-asset-update@stable

.github/workflows/deploy-on-tag-to-svn.yml

@@ -8,7 +8,7 @@ jobs:
     name: New tag
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Composer Install
         uses: php-actions/composer@v6