tablet: Avoid gap between menu and the upper toolbar.

Change-Id: I25845dbe6ddae8f35885b94a9d01902f3a4daa9c
Reviewed-on: https://gerrit.libreoffice.org/c/online/+/91649
Tested-by: Jenkins CollaboraOffice <jenkinscollaboraoffice@gmail.com>
Reviewed-by: Jan Holesovsky <kendy@collabora.com>

loleaflet/css/device-tablet.css

@@ -30,3 +30,8 @@
 	-o-transform: rotate(180deg);
 	transform: rotate(180deg);
 }
+
+/* Additions for the main menu. */
+.main-nav {
+    margin: 0;
+}