Workbench: Another stab at fixing PDM and its plugins.

I think that it was pdm-publish (that hasn't been updated for over 2
years) that's causing the issue. It requires an older version of PDM and
because of that it's breaking the installation of pdm-version and leaves
PDM broken (pipx downgrades PDM but the dependencies aren't installed
properly). Just a theory, let's check.

workbench/Dockerfile

@@ -233,7 +233,7 @@ RUN apt-get update && \
     pipx install chalice && \
     pipx install curator-opensearch && \
     pipx install pdm && \
-    pipx inject pdm six pdm-packer pdm-publish && \
+    pipx inject pdm pdm-packer pdm-version && \
     npm install --global \
         corepack \
         @playwright/test \