大神们，想把默认官方的搜索下拉去掉，让默认只搜索一个模块 ，怎么改？

<div class="page-header-search">
                            <form class="search-form" action="/index.php" method="get">
                                <input type="hidden" name="s" value="api">
                                <input type="hidden" name="c" value="api">
                                <input type="hidden" name="m" value="search">
                                <input type="hidden" name="dir" id="dr_search_module_dir" >
                                <div class="input-group">
                                    <div class="input-group-btn btn-group">
                                        <button id="dr_search_module_name" type="button" class="btn default dropdown-toggle" data-toggle="dropdown" aria-expanded="false">
                                            <i class="fa fa-angle-down"></i>
                                        </button>
                                        <ul class="dropdown-menu">
                                            <!--这是来列出全部可以搜索的内容模块-->
                                            {php $top_search=[];}
                                            {cache name=module-content}
                                            {if $t.search}
                                            {php !$top_search && $top_search=$t;}
                                            <li><a href="javascript:dr_search_module_select('{$t.dirname}', '{$t.name}');"> {$t.name} </a></li>
                                            {/if}
                                            {/cache}
                                        </ul>
                                    </div>
                                    <input type="text" placeholder="搜索内容..." name="keyword" class="fc-search-keyword form-control">
                                    <div class="input-group-btn">
                                        <button class="btn default" type="submit"> <i class="fa fa-search"></i> </button>
                                    </div>
                                </div>
                                <script>
                                    // 这段js是用来执行搜索的
                                    function dr_search_module_select(dir, name) {
                                        $("#dr_search_module_dir").val(dir);
                                        $("#dr_search_module_name").html(name+' <i class="fa fa-angle-down"></i>');
                                    }
                                    dr_search_module_select('{php echo defined('MOD_DIR') ? MOD_DIR : $top_search.dirname}', '{php echo defined('MOD_DIR') ? MODULE_NAME : $top_search.name}');
                                </script>
                            </form>
                        </div>

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