Simplify boolean logic for toggleAttribute()

dom.bs

@@ -6606,20 +6606,19 @@ method, when invoked, must run these steps:
   <p>If <var>attribute</var> is null, then:
 
   <ol>
-   <li><p>If <var>force</var> is not given or is true, create an <a>attribute</a> whose
+   <li><p>If <var>force</var> is given and is false, return false.
+
+   <li><p>Create an <a>attribute</a> whose
    <a for="Attr">local name</a> is <var>qualifiedName</var>, <a for=Attr>value</a> is the empty
    string, and <a for=Node>node document</a> is the <a>context object</a>'s
    <a for=Node>node document</a>, then <a lt="append an attribute">append</a> this <a>attribute</a>
    to the <a>context object</a>, and then return true.
-
-   <li><p>Return false.
   </ol>
 
- <li><p>Otherwise, if <var>force</var> is not given or is false,
- <a lt="remove an attribute by name">remove an attribute</a> given <var>qualifiedName</var> and the
- <a>context object</a>, and then return false.
+ <li><p>Otherwise, if <var>force</var> is given and is true, return true.
 
- <li><p>Return true.
+ <li><p><a lt="remove an attribute by name">Remove an attribute</a> given <var>qualifiedName</var> and the
+ <a>context object</a>, and then return false.
 </ol>
 
 <p>The