Bump actions/checkout from 2 to 2.3.4 (#453)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 2.3.4.
- [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...v2.3.4)

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

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

.github/workflows/build.yml

@@ -18,7 +18,7 @@ jobs:
     env:
       DOCKER_BUILDKIT: "1"
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
 
       - name: Linting
         run: docker build --target lint .
@@ -61,7 +61,7 @@ jobs:
     needs: [verify]
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
 
       - uses: docker/setup-qemu-action@v1
       - uses: docker/setup-buildx-action@v1