Clean up `HTMLSelectElement::setOptionsChangedOnRenderer`
https://bugs.webkit.org/show_bug.cgi?id=306685
rdar://169334265

Reviewed by Anne van Kesteren.

The #if conditions are redundant. `HTMLSelectElement::createElementRenderer` should create the correct renderers for all platforms.

downcast should assert if the wrong renderer is created on iOS.`

* Source/WebCore/html/HTMLSelectElement.cpp:
(WebCore::HTMLSelectElement::setOptionsChangedOnRenderer):

Canonical link: https://commits.webkit.org/306562@main
diff --git a/Source/WebCore/html/HTMLSelectElement.cpp b/Source/WebCore/html/HTMLSelectElement.cpp
index 4e9bf03..22a6921 100644
--- a/Source/WebCore/html/HTMLSelectElement.cpp
+++ b/Source/WebCore/html/HTMLSelectElement.cpp
@@ -816,14 +816,10 @@
 void HTMLSelectElement::setOptionsChangedOnRenderer()
 {
     if (CheckedPtr renderer = this->renderer()) {
-#if !PLATFORM(IOS_FAMILY)
         if (auto* renderMenuList = dynamicDowncast<RenderMenuList>(*renderer))
             renderMenuList->setOptionsChanged(true);
         else
             downcast<RenderListBox>(*renderer).setOptionsChanged(true);
-#else
-        downcast<RenderMenuList>(*renderer).setOptionsChanged(true);
-#endif
     }
 
 #if !PLATFORM(IOS_FAMILY)