Consitently use dbus::utility types

This saves about 4k on the binary size

Tested: Redfish service validator passes.

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: I9546227a19c691b1aecb80e80307889548c0293f
diff --git a/redfish-core/include/utils/collection.hpp b/redfish-core/include/utils/collection.hpp
index c5d603a..2cb2f3d 100644
--- a/redfish-core/include/utils/collection.hpp
+++ b/redfish-core/include/utils/collection.hpp
@@ -30,9 +30,9 @@
 {
     BMCWEB_LOG_DEBUG << "Get collection members for: " << collectionPath;
     crow::connections::systemBus->async_method_call(
-        [collectionPath,
-         aResp{std::move(aResp)}](const boost::system::error_code ec,
-                                  const std::vector<std::string>& objects) {
+        [collectionPath, aResp{std::move(aResp)}](
+            const boost::system::error_code ec,
+            const dbus::utility::MapperGetSubTreePathsResponse& objects) {
             if (ec == boost::system::errc::io_error)
             {
                 aResp->res.jsonValue["Members"] = nlohmann::json::array();