build: github action setup-python upgrade to v2

Author: weakish

.github/workflows/pythonpackage.yml

@@ -18,19 +18,14 @@ on:
       - 'doc/**'
 
 jobs:
-  build:
-
+  lint:
     runs-on: ubuntu-latest
-    strategy:
-      matrix:
-        python-version: [3.5]
-
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python ${{ matrix.python-version }}
-      uses: actions/setup-python@v1
+    - name: Set up Python 
+      uses: actions/setup-python@v2
       with:
-        python-version: ${{ matrix.python-version }}
+        python-version: '3.5'
     - name: Install dependencies
       run: |
         python -m pip install --upgrade pip