Update matches on scrollbar border styles

Author: jackycute

addon/search/matchesonscrollbar.css

@@ -1,7 +1,6 @@
 .CodeMirror-search-match {
   background: gold;
-  border-top: 1px solid orange;
-  border-bottom: 1px solid orange;
+  border: 1px solid orange;
   -moz-box-sizing: border-box;
   box-sizing: border-box;
   opacity: .5;