rm unused 'using'

Device/IO/DataFormatUtil.cpp

@@ -23,8 +23,6 @@
 
 namespace {
 
-using createAxisFun = std::function<Scale*(std::istringstream iss)>;
-
 const std::string GzipExtension = ".gz";
 const std::string BzipExtension = ".bz2";
 const std::string IntExtension = ".int";