Caption should inherit background from table

Since we are fiddling with the default display of table's we need
to declare background of captions explicitly to avoid glitchy
behaviour.

Bug: T170344
Change-Id: I0797d346315c87861075f273baac5acf4e9998cb

resources/skins.minerva.tablet.styles/common.less

@@ -98,6 +98,7 @@ A file for css that optimises the Minerva skin on larger devices.
 			display: table;
 			width: auto !important;
 			caption {
+				background: inherit; // T170344
 				display: table-caption;
 			}
 			tbody {