Rename sdbusplus::message::variant -> std::variant

This was removed from sdbusplus and now breaks the build without
conversion.

Change-Id: I084ede89ca200d3f9bc38d451e54d511418f7cda
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/ipmi/manualcmds.cpp b/ipmi/manualcmds.cpp
index 415262e..3a98c99 100644
--- a/ipmi/manualcmds.cpp
+++ b/ipmi/manualcmds.cpp
@@ -54,7 +54,7 @@
 static constexpr auto propertiesintf = "org.freedesktop.DBus.Properties";
 
 using Property = std::string;
-using Value = sdbusplus::message::variant<bool>;
+using Value = std::variant<bool>;
 using PropertyMap = std::map<Property, Value>;
 
 /* The following was copied directly from my manual thread handler. */
@@ -174,7 +174,7 @@
         return IPMI_CC_INVALID;
     }
 
-    using Value = sdbusplus::message::variant<bool>;
+    using Value = std::variant<bool>;
 
     const auto request =
         reinterpret_cast<const struct FanCtrlRequestSet*>(&reqBuf[0]);