sdbusplus: replace message::variant with std::variant

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If20545ad78b4b813e7bba0909c99fa7156a00c96
diff --git a/user_mgr.hpp b/user_mgr.hpp
index e25ca87..7200c09 100644
--- a/user_mgr.hpp
+++ b/user_mgr.hpp
@@ -47,8 +47,7 @@
 
 using DbusUserObjPath = sdbusplus::message::object_path;
 
-using DbusUserPropVariant =
-    sdbusplus::message::variant<Privilege, ServiceEnabled>;
+using DbusUserPropVariant = std::variant<Privilege, ServiceEnabled>;
 
 using DbusUserObjProperties =
     std::vector<std::pair<PropertyName, DbusUserPropVariant>>;