fix pytest command

Author: blink1073

.github/workflows/build.yml

@@ -40,7 +40,7 @@ jobs:
       - name: Test the extension
         working-directory: jupyter-widget-testwidgets
         run: |
-          pytest
+          python -m pytest
           yarn run lint:check
           yarn run test
 

{{cookiecutter.github_project_name}}/.github/workflows/build.yml

@@ -27,10 +27,8 @@ jobs:
       - name: Test the extension
         run: |
           python -m pip install --upgrade -v -e ".[test, examples, docs]"
-          yarn
+          python -m pytest
           yarn run lint:check
-
-          pytest
           yarn run test
 
       - name: Check docs can be build + links