Remove official level filter from advanced search

User testing has shown this filter isn't really useful and sometimes
makes users wonder what it's about. This is particularly true in CONSUL
installations which don't change the default values (most of them),
since users will see a filter with options like "Official position 1".

app/assets/stylesheets/advanced_search.scss

@@ -6,12 +6,12 @@
   @include breakpoint(large) {
     .filter {
       @include grid-column;
-      width: 25%;
+      width: 33%;
     }
 
     .date-filters {
       float: left;
-      width: 25%;
+      width: 33%;
 
       .filter {
         width: 100%;
@@ -23,7 +23,7 @@
     }
 
     .submit {
-      width: 25%;
+      width: 33%;
     }
   }