Update spec/locale.html

Co-authored-by: Richard Gibson <richard.gibson@gmail.com>

Author: FrankYFTang

spec/locale.html

@@ -693,7 +693,7 @@ <h1>
       </emu-alg>
     </emu-clause>
 
-    <emu-clause id="sec-numberingsystemsoflocale" type="abstract operation">
+    <emu-clause id="sec-numberingsystemsoflocale" type="implementation-defined abstract operation">
       <h1>
         NumberingSystemsOfLocale (
           _loc_: an Intl.Locale,