Bump actions/checkout from 5 to 6 (#539)

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

Author: dependabot[bot]

.github/workflows/deploy.yml

@@ -14,7 +14,7 @@ jobs:
     timeout-minutes: 70
     steps:
       - name: Checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Composer dependencies
         run: composer install --no-dev --no-interaction --optimize-autoloader
       - name: Composer build

.github/workflows/plugin-check.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Composer dependencies
         run: composer install --no-dev --no-interaction --optimize-autoloader
       - name: Build

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Composer dependencies
         run: composer install
       - name: Run Testsuite
@@ -19,7 +19,7 @@ jobs:
     if: github.ref == 'refs/heads/master'
     steps:
       - name: Checkout project
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Composer dependencies
         run: composer install
       - name: Run Testsuite