fix(ui): hide dropdown panels in server-rendered markup

packages/ui/components/Dropdown.wrn

@@ -184,7 +184,7 @@ items: unknown[] = []
         <button
           type="button"
           class="wrn-dropdown__dismiss-layer"
-          data-show='{open || visible}'
+          hidden='{!(open || visible)}'
           aria-label="Close menu"
           @click='hideMenu("outside", event)'
         ></button>
@@ -193,7 +193,7 @@ items: unknown[] = []
       <div
         class="wrn-dropdown__panel"
         data-wrn-anchored="true"
-        data-show='{open || visible}'
+        hidden='{!(open || visible)}'
         role="menu"
         aria-label='{menuLabel}'
       >