[pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

.github/workflows/ci-docs.yml

@@ -16,14 +16,14 @@ jobs:
     runs-on: ubuntu-20.04
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.7
+      - name: Set up Python 3.8
         uses: actions/setup-python@v2
         with:
-          python-version: "3.7"
+          python-version: "3.8"
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install -c .constraints/py3.7.txt .[doc]
+          pip install -c .constraints/py3.8.txt .[doc]
           sudo apt-get -y install graphviz pandoc
       - name: Build documentation and run notebooks
         working-directory: docs