Update index.bs

Co-authored-by: Nan Lin <80365263+linnan-github@users.noreply.github.com>

Author: apasel422

index.bs

@@ -2333,7 +2333,7 @@ an [=aggregation coordinator=] |aggregationCoordinator|, and a [=moment=] |now|:
 
 To <dfn>obtain a set of possible trigger states</dfn> given a [=randomized response output configuration=] |config|:
 1. Let |possibleTriggerStates| be a new [=set=].
-1. [=set/iterate|For each=] |triggerData| |config|'s [=randomized response output configuration/trigger data=]:
+1. [=set/iterate|For each=] |triggerData| of |config|'s [=randomized response output configuration/trigger data=]:
     1. [=list/For each=] |reportWindow| of |config|'s [=randomized response output configuration/event-level report windows=]:
         1. Let |state| be a new [=trigger state=] with the items:
             : [=trigger state/trigger data=]