Bump actions/checkout from 2 to 2.3.4 (#83)

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

@@ -10,7 +10,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v2.3.4
         with:
           ref: ${{ github.event.pull_request.head.sha }}
       - name: Set up Python
@@ -26,7 +26,7 @@ jobs:
       matrix:
         python-version: [3.7, 3.8, 3.9]
     steps:
-      - uses: actions/checkout@v2.3.2
+      - uses: actions/checkout@v2.3.4
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v2.2.2
         with: