Bump actions/checkout from 2.4.0 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2.4.0 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2.4.0...v3)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/main.yaml

@@ -16,7 +16,7 @@ jobs:
       matrix:
         python-version: [3.7, 3.8, 3.9]
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3
       - name: Setup Python
         uses: actions/setup-python@v3
         with:
@@ -49,7 +49,7 @@ jobs:
       matrix:
         python-version: [3.8, 3.9]
     steps:
-      - uses: actions/checkout@v2.4.0
+      - uses: actions/checkout@v3
       - name: Setup Python
         uses: actions/setup-python@v3
         with: