remove umd section from readme

we no longer distribute umd releases

README.md

@@ -62,10 +62,6 @@ replacement for most uses of XMLHttpRequest in traditional web applications.
 npm install whatwg-fetch --save
 ```
 
-As an alternative to using npm, you can obtain `fetch.umd.js` from the
-[Releases][] section. The UMD distribution is compatible with AMD and CommonJS
-module loaders, as well as loading directly into a page via `<script>` tag.
-
 You will also need a Promise polyfill for [older browsers](https://caniuse.com/promises).
 We recommend [taylorhakes/promise-polyfill](https://github.com/taylorhakes/promise-polyfill)
 for its small size and Promises/A+ compatibility.