Block egress in CI and update dependencies

[danyeaw]

• Drop testing with Python 3.8
• Block egress traffic with CI instead of only auditing
• Update pre-commit hooks and other dependencies

PR Checklist

Please check if your PR fulfills the following requirements:

• [X] I have read, and I am following the Contributor guide
• [X] I have read and understand the Code of Conduct

PR Type

What kind of change does this PR introduce?

• [ ] Bugfix
• [ ] Feature
• [ ] Code style update (formatting, local variables)
• [X] Refactoring (no functional changes, no api changes)
• [ ] Documentation content changes

What is the current behavior?

Issue Number: N/A

What is the new behavior?

Does this PR introduce a breaking change?

• [ ] Yes
• [ ] No

Other information