Bump actions/checkout from 3 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...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/build-zip.yml

@@ -8,7 +8,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout files
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
       - name: Create zip
         run: |
           git archive --format=zip --worktree-attributes -9 -o ${{ github.event.repository.name }}.zip HEAD

.github/workflows/prepare-release-branch.yml

@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout the code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           token: ${{ secrets.GH_BOT_PUSH }}
       - name: Maybe use the version number from inputs

.github/workflows/tests-plugin-checker.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v6
 
       - name: Run plugin check
         uses: wordpress/plugin-check-action@v1

.github/workflows/wordpress-plugin-deploy.yml

@@ -11,7 +11,7 @@ jobs:
       shell: bash
       run: echo "PLUGIN_VERSION=$(jq -r .version package.json)" >> $GITHUB_ENV
     - name: Checkout the code
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
     - name: WordPress Plugin Deploy
       uses: 10up/action-wordpress-plugin-deploy@master
       env:

.github/workflows/wporg-update-versions.yml

@@ -31,7 +31,7 @@ jobs:
           echo minimum_wp_version: ${{ github.event.inputs.minimum_wp_version }}
           echo minimum_php_version: ${{ github.event.inputs.minimum_php_version }}
       - name: Checkout the code
-        uses: actions/checkout@v4
+        uses: actions/checkout@v6
         with:
           token: ${{ secrets.GH_BOT_PUSH }}
       - name: Check the version number from package.json