Help: Fix compilation

Change-Id: I2aa1c4d32cc4281da5d4f5374d0a189a1465247c
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/help/searchtaskhandler.cpp

@@ -34,6 +34,7 @@
 #include <QAction>
 #include <QApplication>
 #include <QClipboard>
+#include <QUrl>
 
 using namespace Help::Internal;