Bump actions/checkout from v2.3.3 to v2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from v2.3.3 to v2.3.4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2.3.3...5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f)

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/labels_sync.yaml

@@ -8,7 +8,7 @@ jobs:
     name: Sync labels
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2.3.3
+      - uses: actions/checkout@v2.3.4
       - uses: lannonbr/issue-label-manager-action@2.0.0
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}