Fix ObservableArray example

It showed the wrong output for JSON.stringify().

Author: domenic

index.bs

@@ -6740,7 +6740,7 @@ There is no way to represent a constant observable array value in IDL.
 The [=type name=] of an observable array type is the concatenation of the type name for |T| and the
 string "<code>ObservableArray</code>".
 
-<div class="example" id="example-af5d265e">
+<div class="example" id="example-observable-array" oldids="example-af5d265e">
     The following [=IDL fragment=] defines an [=interface=] with an observable array attribute:
 
     <pre highlight="webidl">
@@ -6818,8 +6818,8 @@ string "<code>ObservableArray</code>".
         console.assert(Array.isArray(building.employees));
         console.assert(building.employees.constructor === Array);
 
-        // Even is treated as an array by JSON.stringify!
-        console.assert(JSON.stringify(building.employees) === `["object Employee"]`);
+        // Even is treated as an array by JSON.stringify! (Note the outer []s.)
+        console.assert(JSON.stringify(building.employees) === `[{}]`);
     </pre>
 </div>