Fix extra outlines in next/prev buttons.

Author: demiankatz

src/content-handlers/iiif/modules/uv-openseadragoncenterpanel-module/css/styles.less

@@ -105,6 +105,9 @@
           &:focus-visible {
             outline: 2px solid @link-color;
             outline-offset: -2px;
+            i, span {
+              outline: 0px;
+            }
           }
         }