PIPE-2997: Additional update/fixes to the workflow template
* `shell:` is evaluated at workflow parse time, not at runtime, so `${{ inputs.pixi_env }}` isn't available in the shell: field for reusable workflows.
* Disable caching for Pixi environment to ensure the latest dev snapshots are used
* Fix a bug in the CASA config stage of the Pixi template
* Remove unnecessary solve-group entries
* Update `protobuf` version specification in `environment.yml` to ensure compatibility with `casaplotms`
