Change CSSMathNegate.type to be same as type of its argument.

Author: darrnshn

css-typed-om/Overview.bs

@@ -1699,8 +1699,10 @@ of all the "math" operations.
             of each of the [=list/items=] in its {{CSSMathProduct/values}} internal slot.
 
         : {{CSSMathNegate}}
+        :: The [=type=] is the same as the [=type=] of its {{CSSMathNegate/values}} internal slot.
+
         : {{CSSMathInvert}}
-        :: The [=type=] is the same as the [=type=] of its {{CSSMathNegate/value}} internal slot,
+        :: The [=type=] is the same as the [=type=] of its {{CSSMathInvert/value}} internal slot,
             but with all [=map/values=] negated.
     </dl>
 </div>