Make message previews more legible

Author: nadonomy

res/themes/light/css/_light.scss

@@ -183,7 +183,7 @@ $roomlist2-button-bg-color: #fff; // Buttons include the filter box, explore but
 $roomlist2-bg-color: rgba(245, 245, 245, 0.90);
 $roomsublist2-divider-color: $primary-fg-color;
 
-$roomtile2-preview-color: #9e9e9e;
+$roomtile2-preview-color: #737D8C;
 $roomtile2-default-badge-bg-color: #61708b;
 $roomtile2-selected-bg-color: #FFF;