fix the regular expression for function clean in utils.js (#4770)

Author: yetingli

lib/utils.js

@@ -76,7 +76,7 @@ exports.clean = function (str) {
     .replace(/^\uFEFF/, '')
     // (traditional)->  space/name     parameters    body     (lambda)-> parameters       body   multi-statement/single          keep body content
     .replace(
-      /^function(?:\s*|\s+[^(]*)\([^)]*\)\s*\{((?:.|\n)*?)\s*\}$|^\([^)]*\)\s*=>\s*(?:\{((?:.|\n)*?)\s*\}|((?:.|\n)*))$/,
+      /^function(?:\s*|\s[^(]*)\([^)]*\)\s*\{((?:.|\n)*?)\}$|^\([^)]*\)\s*=>\s*(?:\{((?:.|\n)*?)\}|((?:.|\n)*))$/,
       '$1$2$3'
     );