python-pipx: update to 1.12.0

python-pipx: update to 1.12.0

New features (pipx 1.12.0):
- Add --fetch-python / PIPX_FETCH_PYTHON env var (always|missing|never)
  to control standalone Python interpreter downloads
- Add opt-in "uv" backend: pipx can now use "uv venv" and "uv pip" for
  managing virtual environments
  * When "uv" is on PATH, defaults to using uv for NEW venvs
  * Existing venvs keep their recorded backend (pip or uv)
  * Set PIPX_DEFAULT_BACKEND=pip to force pip even with uv available
  * pipx install pip always uses the pip backend (uv venvs have no pip)

Deprecations:
- --fetch-missing-python and PIPX_FETCH_MISSING_PYTHON deprecated;
  use --fetch-python=missing or PIPX_FETCH_PYTHON=missing instead

Changelog:
https://github.com/pypa/pipx/releases/tag/1.12.0

Signed-off-by: Alexandru Ardelean <redacted>