Moved into one build to have coverage

Author: JonathanHuot

.github/workflows/run-tests.yml

@@ -16,15 +16,13 @@ jobs:
           - python-version: 3.6
             tox-env: py36
           - python-version: 3.7
-            tox-env: py37,docs,readme
+            tox-env: py37,docs,readme,black
           - python-version: 3.8
             tox-env: py38
           - python-version: 3.9
             tox-env: py39
           - python-version: pypy3
             tox-env: pypy3
-          - python-version: 3.7
-            tox-env: black
     steps:
     - uses: actions/checkout@v2
     - name: Set up Python ${{ matrix.python-version }}