remove usage of sdbusplus::message::variant

sdbusplus has had its alias of std::variant in place for long
enough. This changes all ipmid references to use std::variant
directly instead of the sdbusplus alias.

Tested-by: building and running ipmid

Change-Id: Id5b4136d4589aa598815edd3ef4202e64a7698e2
Signed-off-by: Vernon Mauery <vernon.mauery@linux.intel.com>
diff --git a/user_channel/user_mgmt.hpp b/user_channel/user_mgmt.hpp
index 857be99..8061482 100644
--- a/user_channel/user_mgmt.hpp
+++ b/user_channel/user_mgmt.hpp
@@ -23,12 +23,13 @@
 #include <cstdint>
 #include <ctime>
 #include <sdbusplus/bus.hpp>
+#include <variant>
 
 namespace ipmi
 {
 
 using DbusUserPropVariant =
-    sdbusplus::message::variant<std::vector<std::string>, std::string, bool>;
+    std::variant<std::vector<std::string>, std::string, bool>;
 
 using DbusUserObjPath = sdbusplus::message::object_path;