left_sidebar: Fix the opacity of group,bot icons.

This commit fixes the opacity of the group-icon and bot-icon
in the left-sidebar direct message section to make them look
 more consistent with the other icons in the left sidebar.

web/styles/left_sidebar.css

@@ -256,6 +256,10 @@ li.show-more-topics {
 
             .pm_left_col {
                 min-width: $left_col_size;
+
+                & span:not(.user_circle) {
+                    opacity: 0.7;
+                }
             }
         }