Use `--group dev` instead of `--dev` flag for poetry package installation

[karrtikr]

#19980

[karrtikr]

Verification steps:

• Use pre-release
• Install poetry: https://github.com/python-poetry/poetry#installation
• Create and open poetry workspace: https://python-poetry.org/docs/basic-usage/#project-setup
• Use poetry shell to create an env if not already created.
• Select the create environment using Python: Select Interpreter command
• Attempt to format using the Python extension, you should be prompted to install black.
• Click Install and verify it uses --group option instead of --dev.

@SaidBySolo Can you help verify this?

[SaidBySolo]

@karrtikr It works as intended :D

v2022.17.12971017

[karrtikr]

Thanks for verifying!