[LyX/2.1.x] Remove unneeded header

[Enrico Forestieri]

commit 5f1c593175e94590373411151f5ef215887e3944
Author: Enrico Forestieri <for...@lyx.org>
Date:   Mon Jul 6 23:49:56 2015 +0200

    Remove unneeded header
    
    Forgot this at e473ee8b

diff --git a/src/mathed/MathMacro.cpp b/src/mathed/MathMacro.cpp
index ba84736..bc942be 100644
--- a/src/mathed/MathMacro.cpp
+++ b/src/mathed/MathMacro.cpp
@@ -22,7 +22,6 @@
 #include "MathSupport.h"
 
 #include "Buffer.h"
-#include "BufferList.h"
 #include "BufferView.h"
 #include "CoordCache.h"
 #include "Cursor.h"