Normalize Internal Slots of Intl.Collator by stating that [[SortLocal…

…eData]].[[<locale>]].[[co]] and [[SearchlocaleData]].[[<locale>]].[[co]] are Lists of Strings which must have *null* as their first elements.

spec/collator.html

@@ -121,7 +121,7 @@ <h1>Internal slots</h1>
       </p>
 
       <ul>
-        <li>The first element of [[SortLocaleData]].[[&lt;_locale_&gt;]].[[co]] and [[SearchLocaleData]].[[&lt;_locale_&gt;]].[[co]] must be *null*.</li>
+        <li>[[SortLocaleData]].[[&lt;_locale_&gt;]].[[co]] and [[SearchLocaleData]].[[&lt;_locale_&gt;]].[[co]] are Lists of Strings. The first element of each of these Lists of Strings must be *null*.
         <li>The values *"standard"* and *"search"* must not be used as elements in any [[SortLocaleData]].[[&lt;_locale_&gt;]].[[co]] and [[SearchLocaleData]].[[&lt;_locale_&gt;]].[[co]] List.</li>
         <li>[[SearchLocaleData]].[[&lt;_locale_&gt;]] must have a [[sensitivity]] field with one of the String values *"base"*, *"accent"*, *"case"*, or *"variant"*.</li>
         <li>[[SearchLocaleData]].[[&lt;_locale_&gt;]] and [[SortLocaleData]].[[&lt;_locale_&gt;]] must have an [[ignorePunctuation]] field with a Boolean value.</li>