This matches the version used in the Gutenberg project. While WordPress core no longer depends on this polyfill as of [50934], this brings the latest updates of the library to anyone still utilizing it. For a full list of changes in this update, see the `whatwg-fetch` GitHub: https://github.com/github/fetch/compare/v3.0.0...v3.6.2 Follow-up to [43719], [50934]. Props hareesh-pillai, rsiddharth, desrosj. Fixes #53929. Built from https://develop.svn.wordpress.org/trunk@51692 git-svn-id: http://core.svn.wordpress.org/trunk@51298 1a063a9b-81f0-0310-95a4-ce76da25c4cd