Clean exported headers of the TextEditor plugin.

Change-Id: I1e7dd34ba5a51fb0b34d137dc03add4457b32ed1
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/texteditor/simplecodestylepreferences.cpp

@@ -30,6 +30,8 @@
 
 #include "simplecodestylepreferences.h"
 
+#include <QVariant>
+
 using namespace TextEditor;
 
 static const char settingsSuffixKey[] = "TabPreferences";