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/sensordatahandler.hpp b/sensordatahandler.hpp
index a7eadda..73f0dbf 100644
--- a/sensordatahandler.hpp
+++ b/sensordatahandler.hpp
@@ -250,7 +250,7 @@
     for (const auto& property : interface->second)
     {
         msg.append(property.first);
-        sdbusplus::message::variant<T> value =
+        std::variant<T> value =
             (cmdData.assertOffset8_14 << 8) | cmdData.assertOffset0_7;
         msg.append(value);
     }
@@ -281,7 +281,7 @@
     for (const auto& property : interface->second)
     {
         msg.append(property.first);
-        sdbusplus::message::variant<T> value = raw_value;
+        std::variant<T> value = raw_value;
         msg.append(value);
     }
     return updateToDbus(msg);