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

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If7c54cfe20a84fa91aacc309ebfa804231078bf7
diff --git a/bmc_state_manager.cpp b/bmc_state_manager.cpp
index 1b7d311..bf10c22 100644
--- a/bmc_state_manager.cpp
+++ b/bmc_state_manager.cpp
@@ -35,7 +35,7 @@
 
 void BMC::discoverInitialState()
 {
-    sdbusplus::message::variant<std::string> currentState;
+    std::variant<std::string> currentState;
     sdbusplus::message::object_path unitTargetPath;
 
     auto method = this->bus.new_method_call(SYSTEMD_SERVICE, SYSTEMD_OBJ_PATH,