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

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: Id94a72c3195a2ffefac9b47eb77cd7748f4e61bc
diff --git a/src/item_updater.cpp b/src/item_updater.cpp
index a5b5afb..5481b06 100644
--- a/src/item_updater.cpp
+++ b/src/item_updater.cpp
@@ -31,10 +31,8 @@
 
 void ItemUpdater::createActivation(sdbusplus::message::message& m)
 {
-    namespace msg = sdbusplus::message;
-
     sdbusplus::message::object_path objPath;
-    std::map<std::string, std::map<std::string, msg::variant<std::string>>>
+    std::map<std::string, std::map<std::string, std::variant<std::string>>>
         interfaces;
     m.read(objPath, interfaces);