Remove cache to see if that helps with pytest-cov issues

.github/workflows/docker-publish.yml

@@ -17,15 +17,6 @@ jobs:
       uses: actions/setup-python@v2
       with:
         python-version: ${{ matrix.python-version }}
-    - name: Get pip cache dir
-      id: pip-cache
-      run: |
-        echo "::set-output name=dir::$(pip cache dir)"
-    - name: Persistent Github pip cache
-      uses: actions/cache@v2
-      with:
-        path: ${{ steps.pip-cache.outputs.dir }}
-        key: ${{ runner.os }}-pip${{ matrix.python-version }}
     - name: Update system, install system requirements
       run: |
         sudo apt-get update -qq