Update default install guidance

For several years, the recommended distribution has been encumbered by vague terms of service which are unsuitable for many readers of the documentation.

Following these instructions can expose a user (or the organization that owns their IP address) to legal action.

Further, Project Jupyter has no ability to influence the versions of Jupyter software included in the recommended distribution, which can be missing security updates.

Short Term

• hide these instructions behind a scary warning and <details> reveal
• remove these instructions entirely, recommending a path starting with:
  • an official python release, and "stdlib" (pip/venv) guidance
  • a miniforge installer, and mamba env update guidance

Long Term

• provide, at a minimum, an updated jupyter metapackage (e.g. with lab) as the seed for a full installer including
  • notebook
  • lab
  • self-hosted documentation for the jupyter software you get
• document this as the recommended installation
• provide a community-driven way to encourage customizing Jupyter for specific user groups
  • Jupyter for Jupyter Contributors
  • Jupyter for Scientific Documentation
  • etc.