simplify a regex

Author: zloirock

packages/core-js/modules/esnext.json.parse.js

@@ -30,7 +30,7 @@ var push = uncurryThis([].push);
 
 var IS_DIGIT = /^\d$/;
 var IS_NON_ZERO_DIGIT = /^[1-9]$/;
-var IS_NUMBER_START = /^(?:-|\d)$/;
+var IS_NUMBER_START = /^[\d-]$/;
 var IS_WHITESPACE = /^[\t\n\r ]$/;
 
 var PRIMITIVE = 0;