WebUI: Use vanilla JS to create elements

All elements are now created using createElement() method:
https://developer.mozilla.org/en-US/docs/Web/API/Document/createElement

PR #21975.

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Co-authored-by: Chocobo1 <Chocobo1@users.noreply.github.com>

src/webui/www/private/scripts/download.js

@@ -48,7 +48,7 @@ window.qBittorrent.Download ??= (() => {
                             continue;
 
                         const category = data[i];
-                        const option = new Element("option");
+                        const option = document.createElement("option");
                         option.value = category.name;
                         option.textContent = category.name;
                         $("categorySelect").appendChild(option);