Tiny Regex improvements

Summary: Recreation of D22118786, which was so old rebasing died on some lacking meta data. Lands https://github.com/facebook/flipper/pull/1256

Reviewed By: passy

Differential Revision: D24331424

fbshipit-source-id: 65fc5d8bf0242d4266e269716a319d71ce2e2826

desktop/babel-transformer/src/fb-stubs.ts

@@ -15,7 +15,7 @@ const isFBFile = (filePath: string) =>
   filePath.includes(`${path.sep}fb${path.sep}`);
 
 const requireFromFolder = (folder: string, path: string) =>
-  new RegExp(folder + '/[\\w.-_]+(.js)?$', 'g').test(path);
+  new RegExp(folder + '/[\\w.-]+(.js)?$', 'g').test(path);
 
 module.exports = () => ({
   name: 'replace-fb-stubs',