Update function.md

勘误。line:766
原：return person.first + ' ' + person.name;
改：return person.first + ' ' + person.last;

docs/function.md

@@ -763,7 +763,7 @@ const full = ({ first, last }) => first + ' ' + last;
 
 // 等同于
 function full( person ){
-  return person.first + ' ' + person.name;
+  return person.first + ' ' + person.last;
 }
 ```