Add missing include.

git-svn-id: http://root.cern.ch/svn/root/trunk@29143 27541ba8-7e3a-0410-8455-c3a389f83636

tutorials/roofit/rf610_visualerror.C

@@ -19,6 +19,7 @@
 #include "RooAddPdf.h"
 #include "RooPlot.h"
 #include "TCanvas.h"
+#include "TAxis.h"
 using namespace RooFit ;