Update indexOfAll snippet return type

Now we're just going to return an empty array. This keeps a consistent return type, does not need checking, and won't break api chaining.

Decision was made because otherwise you'd have to add a filter step or check if the return is not an array. Instead we just want an empty array so it has a consistent API, and no indeces is a valid amount

snippets/indexOfAll.md

@@ -9,11 +9,11 @@ Return `[-1]` if `length` of the array of indices is `0`, otherwise return the a
 const indexOfAll = (arr, val) => {
   const indices = [];
   arr.forEach((el, i) => el === val && indices.push(i));
-  return indices.length ? indices : [-1];
+  return indices;
 };
 ```
 
 ```js
 indexOfAll([1, 2, 3, 1, 2, 3], 1); // [0,3]
-indexOfAll([1, 2, 3], 4); // [-1]
+indexOfAll([1, 2, 3], 4); // []
 ```