misc/py-shell-gpt: update to 0.9.0

While here:

• switch to USE_PYTHON=pep517
• remove commented do-test target since it's already supported by USE_PYTHON=pytest

Changelog:

• https://github.com/TheR1D/shell_gpt/releases/tag/0.8.9
• https://github.com/TheR1D/shell_gpt/releases/tag/0.9.0

Reported by: GitHub (watch releases)