WebUI: use native function to convert to numbers

Also replace `parseInt()` since `Number()` behavior is more intuitive.

PR #21831.

src/webui/www/private/uploadlimit.html

@@ -35,7 +35,7 @@
 
         const hashes = new URI().getData("hashes").split("|");
         const setUpLimit = () => {
-            const limit = $("uplimitUpdatevalue").value.toInt() * 1024;
+            const limit = Number($("uplimitUpdatevalue").value) * 1024;
             if (hashes[0] === "global") {
                 new Request({
                     url: "api/v2/transfer/setUploadLimit",