Bump actions/setup-python from 2 to 4

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 2 to 4.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v2...v4)

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

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

Author: dependabot[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - uses: actions/setup-python@v2
+    - uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
     - run: python -m pip install --upgrade pip setuptools codecov