Bump actions/checkout from 4 to 6 (#38393)

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...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/beam_PostCommit_Python_Versions.yml

@@ -88,7 +88,7 @@ jobs:
       (github.event_name == 'schedule' && github.repository == 'apache/beam') ||
       github.event_name == 'workflow_dispatch'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Setup repository
         uses: ./.github/actions/setup-action
         with:

.github/workflows/beam_PreCommit_Java_Dataflow.yml

@@ -77,7 +77,7 @@ jobs:
       github.event_name == 'workflow_dispatch' ||
       github.event.comment.body == 'Run Java Dataflow Non-portable Worker PreCommit'
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
       - name: Setup repository
         uses: ./.github/actions/setup-action
         with:

.github/workflows/deploy_release_candidate_pypi.yaml

@@ -30,7 +30,7 @@ jobs:
         PYPI_API_TOKEN=$(jq -r '.inputs.PYPI_API_TOKEN' $GITHUB_EVENT_PATH)
         echo "::add-mask::$PYPI_API_TOKEN"
     - name: Checkout
-      uses: actions/checkout@v4
+      uses: actions/checkout@v6
     - name: Setup environment
       uses: ./.github/actions/setup-environment-action
       with: