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

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ia01b13a33b1cbd96815bd9e91456bcdcf2528742
diff --git a/ext_interface.cpp b/ext_interface.cpp
index f37eab6..a5c1c3c 100644
--- a/ext_interface.cpp
+++ b/ext_interface.cpp
@@ -75,7 +75,7 @@
         // TODO openbmc/openbmc#851 - Once available, throw returned error
         throw std::runtime_error("ERROR in reading BOOTCOUNT");
     }
-    sdbusplus::message::variant<uint32_t> rebootCount;
+    std::variant<uint32_t> rebootCount;
     reply.read(rebootCount);
 
     return std::get<uint32_t>(rebootCount);