docs: update the IPython Magics docs

[ashleyxuu]

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:

• Make sure to open an issue as a bug/issue before writing your code! That way we can discuss the change, evaluate designs, and agree on the general idea
• Ensure the tests and linter pass
• Code coverage does not decrease (if any source code was changed)
• Appropriate docs were updated (if necessary)
  • docs can be viewed in: https://bigframes-swe.teams.x20web.corp.google.com/ashleyxu/html_magics_05/index.html

Fixes #<issue_number_goes_here> 🦕

[tswast]

Thanks!