[ VM / Observatory ] Fixed getInstances invocation still using 'classId' instead of 'objectId' parameter.

Change-Id: I6e56b927b317e685b384949fb2f8554323f71e43
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/108686
Reviewed-by: Siva Annamalai <[email protected]>
Commit-Queue: Ben Konyi <[email protected]>

Author: bkonyi

runtime/observatory/lib/src/service/object.dart

@@ -1907,7 +1907,7 @@ class Isolate extends ServiceObjectOwner implements M.Isolate {
 
   Future<ServiceObject> getInstances(Class cls, var limit) {
     Map params = {
-      'classId': cls.id,
+      'objectId': cls.id,
       'limit': limit.toString(),
     };
     return invokeRpc('getInstances', params);