Minor clarity improvements (#6225)

1. Reworded a sentence from "add" to "change", because new elements can't be added to Typed Arrays
2. Replaced `Array.prototype` with <code>*TypedArray*.prototype</code>, as this page is about the latter.

files/en-us/web/javascript/reference/global_objects/typedarray/slice/index.html

@@ -64,7 +64,7 @@ <h2 id="Description">Description</h2>
 
 <p>The <code>slice</code> method does not alter the original typed array, but instead returns a copy of a portion of the original typed array. As typed arrays only store primitive values, the copy the <code>slice</code> method returns is always a shallow copy.</p>
 
-<p>If a new element is added to either typed array, the other typed array is not affected.
+<p>If an element is changed in either typed array, the other typed array is not affected.
 </p>
 
 <h2 id="Examples">Examples</h2>
@@ -96,7 +96,7 @@ <h2 id="Polyfill">Polyfill</h2>
 
 <p>If you need to support truly obsolete JavaScript engines that don't support
   {{jsxref("Object.defineProperty")}}, it's best not to polyfill
-  <code>Array.prototype</code> methods at all, as you can't make them non-enumerable.</p>
+  <code><em>TypedArray</em>.prototype</code> methods at all, as you can't make them non-enumerable.</p>
 
 <h2 id="Specifications">Specifications</h2>