Bugfix: Rename member output to outputs of MLLstmCellSupportLimits

`MLLstmCellSupportLimits.outputs` reflects that lstmCell returns a
sequence of operands.

Fix webmachinelearning#755 (comment)

index.bs

@@ -4885,7 +4885,7 @@ dictionary MLLstmCellSupportLimits {
   MLSupportLimits bias;
   MLSupportLimits recurrentBias;
   MLSupportLimits peepholeWeight;
-  MLSupportLimits output;
+  MLSupportLimits outputs;
 };
 
 partial dictionary MLOpSupportLimits {
@@ -4947,8 +4947,8 @@ partial dictionary MLOpSupportLimits {
     :: {{MLSupportLimits}} for recurrentBias operand.
     : <dfn>peepholeWeight</dfn>
     :: {{MLSupportLimits}} for peepholeWeight operand.
-    : <dfn>output</dfn>
-    :: {{MLSupportLimits}} for output operand.
+    : <dfn>outputs</dfn>
+    :: {{MLSupportLimits}} for output operands.
 </dl>
 
 {{MLOpSupportLimits}} has following member for {{MLGraphBuilder/lstmCell()}}: