Fixed a hbs linting problem with the Clear Member button

no issue

ghost/admin/app/components/members-activity/member-filter.hbs

@@ -1,9 +1,9 @@
 {{#if @selected}}
-    <div class="gh-btn" {{on "click" (fn @onChange null)}}>
+    <button class="gh-btn" {{on "click" (fn @onChange null)}} type="button">
         <span class="gh-btn-label-green">
             Clear member &times;
         </span>
-    </div>
+    </button>
 {{else}}
     <PowerSelect
         @searchEnabled={{false}}