Replace double tilde with Math.floor (#30691)

Nowadays, browser engines have improved a lot and `Math.floor` is the same, if not faster.
Also, clarity is better than micro-optimizations in this case.

js/src/util/index.js

@@ -26,7 +26,7 @@ const toType = obj => {
 
 const getUID = prefix => {
   do {
-    prefix += ~~(Math.random() * MAX_UID) // "~~" acts like a faster Math.floor() here
+    prefix += Math.floor(Math.random() * MAX_UID)
   } while (document.getElementById(prefix))
 
   return prefix