github: Don't use pip3 to install Python packages anymore

Currently, the runner images enable break-system-packages globally.
However, this workaround will be removed by the end of March.  So
we switch to installing these packages as intended via distro (the
alternative would be to use pipx, at least for tox).

.github/actions/default/action.yml

@@ -5,9 +5,6 @@ runs:
     - name: "Install Dependencies"
       run: ./scripts/test.sh deps
       shell: bash
-    - name: "Install Python Dependencies"
-      run: ./scripts/test.sh pydeps
-      shell: bash
     - name: "Build Dependencies"
       run: ./scripts/test.sh build-deps
       shell: bash