Upgrade Prettier from 1.17 to 2.0.2.

Summary:
This gets us on the latest Prettier 2.x:
https://prettier.io/blog/2020/03/21/2.0.0.html

Notably, this adds support for TypeScript 3.8,
which introduces new syntax, such as `import type`.

Reviewed By: zertosh

Differential Revision: D20636268

fbshipit-source-id: fca5833d003804333a05ba16325bbbe0e06d6c8a

desktop/static/transforms/electron-requires.js

@@ -80,7 +80,7 @@ module.exports = function (babel) {
 
         if (
           BUILTINS.includes(source) ||
-          BUILTINS.some((moduleName) => source.startsWith(`${moduleName}/`))
+          BUILTINS.some(moduleName => source.startsWith(`${moduleName}/`))
         ) {
           path.node.callee.name = 'electronRequire';
         }