chore(deps): update actions/setup-python action to v4 (#419)

* chore(deps): update actions/setup-python action to v4

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Anthonios Partheniou <[email protected]>
Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: 3 people

.github/workflows/mypy.yml

@@ -10,7 +10,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v3
     - name: Setup Python
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: "3.7"
     - name: Install nox

.github/workflows/unittest.yml

@@ -28,7 +28,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v3
     - name: Setup Python
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python }}
     - name: Install nox
@@ -55,7 +55,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v3
     - name: Setup Python
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: "3.10"
     - name: Install coverage