Update GH action step

Signed-off-by: aiordache <anca.iordache@docker.com>

.github/workflows/ci.yml

@@ -19,9 +19,9 @@ jobs:
             - name: Install dependencies
               run: |
                   python -m pip install --upgrade pip
-                  pip install tox tox-gh-actions==2.2.0
-            - name: Test with tox
+                  pip install -r test-requirements.txt -r requirements.txt
+            - name: Test with pytest
               run: |
                   docker logout
                   rm -rf ~/.docker
-                  tox
+                  py.test -v --cov=docker tests/unit