Bump actions/checkout from 2 to 3

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v2...v3)

---
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/ci.yml

@@ -18,7 +18,7 @@ jobs:
 
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Setup Python ${{ matrix.python-version }}
         uses: actions/setup-python@v2.3.2

.github/workflows/pypi.yml

@@ -10,7 +10,7 @@ jobs:
     environment: pypi
     steps:
       - name: Checkout repo
-        uses: actions/checkout@v2
+        uses: actions/checkout@v3
 
       - name: Setup Python 3.9
         uses: actions/setup-python@v2.3.2