build(deps): bump actions/checkout from 1 to 2.3.4

Bumps [actions/checkout](https://github.com/actions/checkout) from 1 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/v1...v2.3.4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/python.yml

@@ -16,7 +16,7 @@ jobs:
   code-format:
     runs-on: ubuntu-20.04
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2.3.4
     - uses: actions/setup-python@v2.2.2
       with:
         python-version: '3.9'
@@ -88,7 +88,7 @@ jobs:
           pandas-version: 0.25.*
       fail-fast: false
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2.3.4
     - uses: actions/setup-python@v2.2.2
       with:
         python-version: ${{ matrix.python-version }}
@@ -131,7 +131,7 @@ jobs:
       run:
         working-directory: examples/
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v2.3.4
     - uses: actions/setup-python@v1
       with:
         python-version: ${{ matrix.python-version }}