Update index.bs

Co-authored-by: Anssi Kostiainen <[email protected]>

Author: inexorabletash

index.bs

@@ -916,7 +916,7 @@ interface MLActivation {
     : <dfn>\[[options]]</dfn> of type [=ordered map=]
     ::
         A dictionary containing {{MLActivation}} options.
-    : <dfn>\[[operator]]</dfn> of type [=platform operator=].
+    : <dfn>\[[operator]]</dfn> of type [=platform operator=]
     ::
         Reference to {{MLActivation}}'s corresponding [=platform operator=].
   </dl>