Switch to side-by-side view

--- a/src/qtgui/recoll.pro.in
+++ b/src/qtgui/recoll.pro.in
@@ -39,7 +39,6 @@
 FORMS	= \
 	advsearch.ui \
 	spell.ui \
-	preview.ui \
 	rclmain.ui \
 	sort.ui \
 	ssearchb.ui \