12.0 optimize user select (#6307)

* 01 remove useless reviewer

* 02 change user select style

* fix code format

frontend/src/components/dialog/sysadmin-dialog/sysadmin-group-add-member-dialog.js

@@ -41,7 +41,6 @@ class SysAdminGroupAddMemberDialog extends React.Component {
           <UserSelect
             ref="userSelect"
             isMulti={true}
-            className="reviewer-select"
             placeholder={gettext('Search users')}
             onSelectChange={this.handleSelectChange}
           />