gh-actions: use python v2

Author: nschloe

.github/workflows/ci.yml

@@ -6,7 +6,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/setup-python@v1
+    - uses: actions/setup-python@v2
       with:
         python-version: "3.x"
     - uses: actions/checkout@v2
@@ -25,7 +25,7 @@ jobs:
       matrix:
         python-version: [3.6, 3.7, 3.8]
     steps:
-    - uses: actions/setup-python@v1
+    - uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
     - uses: actions/checkout@v2