typeahead: Fix stream typeahead flashing before topic typeahead.

Removed a redundant call to bootstrap typeahead's `lookup` function when
the `automated` function returns true, which was causing the streams
typeahead to show up briefly before the topic typeahead on pressing `>`
immediately after a stream name.

web/third/bootstrap-typeahead/typeahead.js

@@ -281,7 +281,6 @@ import {get_string_diff} from "../../src/util";
       }
       if (this.automated()) {
         this.select();
-        this.lookup();
         return this;
       }
       return this.render(items.slice(0, this.options.items)).show()