Remove unused lexical_cast header

Signed-off-by: Ed Tanous <edtanous@google.com>
Change-Id: If3ab888cfb705f7cc1e6f878c64e5f5467a8e82d
diff --git a/src/FanMain.cpp b/src/FanMain.cpp
index 83bb9b6..0f5e721 100644
--- a/src/FanMain.cpp
+++ b/src/FanMain.cpp
@@ -22,7 +22,6 @@
 #include <boost/algorithm/string/replace.hpp>
 #include <boost/container/flat_map.hpp>
 #include <boost/container/flat_set.hpp>
-#include <boost/lexical_cast.hpp>
 #include <sdbusplus/asio/connection.hpp>
 #include <sdbusplus/asio/object_server.hpp>
 #include <sdbusplus/bus/match.hpp>