Update python-mypy.yml

.github/workflows/python-mypy.yml

@@ -11,11 +11,11 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v2
       with:
-        python-version: '3.x'
+        python-version: '3.9'
     - name: Install Dependencies
       run: |
         python -m pip install --upgrade pip
-        pip install mypy
+        python -m pip install mypy
     - name: mypy
       run: |
-        mypy pydualsense/
+        mypy pydualsense/