Fix Windows

src/core/client_config/subchannel_index.c

@@ -115,7 +115,7 @@ void grpc_subchannel_key_destroy(grpc_exec_ctx *exec_ctx,
                                  grpc_subchannel_key *k) {
   grpc_connector_unref(exec_ctx, k->connector);
   gpr_free(k->args.addr);
-  gpr_free(k->args.filters);
+  gpr_free((grpc_channel_args *)k->args.filters);
   grpc_channel_args_destroy((grpc_channel_args *)k->args.args);
   gpr_free(k);
 }