Use false instead of not true

Author: Michael Wilson

index.bs

@@ -1640,7 +1640,7 @@ Constructors</h4>
                 <a href="#validating-sink-identifier">sink identifier validation
                 </a> of {{AudioContext/[[sink ID]]}}.
 
-        1. If |validationResult| is not <code>true</code>, [=Queue a
+        1. If |validationResult| is <code>false</code>, [=Queue a
                 media element task=] to [=fire an event=] named {{AudioContext/error}}
                 at the {{AudioContext}}, and abort the following steps.
 
@@ -2173,7 +2173,7 @@ Methods</h4>
                 <a href="#validating-sink-identifier">sink identifier validation</a>
                 of |sinkId|.
 
-            1. If |validationResult| is not <code>true</code>, return a promise
+            1. If |validationResult| is <code>false</code>, return a promise
                 rejected with a new {{DOMException}} whose name is
                 "{{NotAllowedError}}". Abort these steps.