Make a solution of 1.5.5 task more correct

Proposed solution is in sync with some previous sort function examples. It also makes sorting stable (does not skip `0` result).

1-js/05-data-types/05-array-methods/8-sort-objects/solution.md

@@ -1,6 +1,6 @@
 ```js run no-beautify
 function sortByAge(arr) {
-  arr.sort((a, b) => a.age > b.age ? 1 : -1);
+  arr.sort((a, b) => a.age - b.age);
 }
 
 let john = { name: "John", age: 25 };