Branch protection on main not adhering to best practices

[mapbox-github-ci-issues-5]

👋 Hey there! It's Changebot, and I help repositories follow our engineering best practices. My magic wand found some things I wanted to highlight for your review:

Item	Current status	Best practice guidelines
main branch protection: Dismiss stale pull request approvals when new commits are pushed	Unchecked	Checked

Can you take a look at these best practices and make any adjustments if needed?

Please tag @mapbox/security-and-compliance on this issue if you have any questions