[LyX/master] Remove zombie noncopyable.hpp dependency

[Georg Baum]

commit 0f5554a8f230b9522ff0a1c6e4e0784333ecfdcd
Author: Georg Baum <b...@lyx.org>
Date:   Tue Jun 7 20:49:27 2016 +0200

    Remove zombie noncopyable.hpp dependency
    
    The header was still included, but not used.

diff --git a/src/insets/ExternalTemplate.h b/src/insets/ExternalTemplate.h
index 18d9835..8ba8672 100644
--- a/src/insets/ExternalTemplate.h
+++ b/src/insets/ExternalTemplate.h
@@ -15,8 +15,6 @@
 
 #include "ExternalTransforms.h"
 
-#include <boost/noncopyable.hpp>
-
 #include <vector>
 
 namespace lyx {