Bundled Themes: Update Twenty Twenty.

This brings `trunk`’s version of Twenty Twenty in-sync with GitHub.

For a complete list of changes since [46551], see https://github.com/WordPress/twentytwenty/compare/bc89c51...4549fd9.

Reviewed by SergeyBiryukov, desrosj, ianbelanger.
Props anlino, ianbelanger, poena, williampatton, nielslange, acosmin, intimez, itowhid06, decrecementofeliz, aristath, westonruter, mukesh27, jorgefilipecosta, karmatosed.
Fixes #48386.
Built from https://develop.svn.wordpress.org/trunk@46571


git-svn-id: https://core.svn.wordpress.org/trunk@46368 1a063a9b-81f0-0310-95a4-ce76da25c4cd