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/fb-stubs.js

@@ -12,7 +12,7 @@ const path = require('path');
 const replaceFBStubs = fs.existsSync(
   path.join(__dirname, '..', '..', 'app', 'src', 'fb'),
 );
-const isFBFile = (filePath) => filePath.includes(`${path.sep}fb${path.sep}`);
+const isFBFile = filePath => filePath.includes(`${path.sep}fb${path.sep}`);
 
 const requireFromFolder = (folder, path) =>
   new RegExp(folder + '/[A-Za-z0-9.-_]+(.js)?$', 'g').test(path);