Fix spaces around operator

Author: usernamehw

1-js/02-first-steps/15-function-expressions-arrows/article.md

@@ -403,9 +403,9 @@ If we have only one argument, then parentheses can be omitted, making that even
 
 ```js run
 // same as
-// let double = function(n) { return n*2 }
+// let double = function(n) { return n * 2 }
 *!*
-let double = n => n*2;
+let double = n => n * 2;
 */!*
 
 alert( double(3) ); // 6