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

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I7b2bc0a8b34e4d276c0e8ea2243459aab4e1c177
diff --git a/monitor/fan.hpp b/monitor/fan.hpp
index 663e27e..a581b3b 100644
--- a/monitor/fan.hpp
+++ b/monitor/fan.hpp
@@ -55,7 +55,7 @@
 class Fan
 {
     using Property = std::string;
-    using Value = sdbusplus::message::variant<bool>;
+    using Value = std::variant<bool>;
     using PropertyMap = std::map<Property, Value>;
 
     using Interface = std::string;