[mbo theme] Fix searching style

theme/mbo.css

@@ -30,7 +30,7 @@
  
 .cm-s-mbo .CodeMirror-matchingtag {background: #4e4e4e;}
 
-div.CodeMirror span.CodeMirror-searching {
+.cm-s-mbo span.cm-searching {
   background-color: none;
   background: none;
   box-shadow: 0 0 0 1px #ffffec;