This updates PostCSS related dependencies for the main Core build process to versions that use the latest major version of PostCSS, 8.x.
There were no changes to any versioned CSS files as a result of this update directly. However, two occurrences of `-o-tab-size` have been removed due to the version of `caniuse-lite` used being updated in the process.
See #57554, #57555.
Built from https://develop.svn.wordpress.org/trunk@55150
git-svn-id: http://core.svn.wordpress.org/trunk@54683 1a063a9b-81f0-0310-95a4-ce76da25c4cd
