Remove setImmediate polyfill (#27567)

src/favicon.ts

@@ -194,9 +194,9 @@ export default class Favicon {
     }
 
     private setIcon(canvas: HTMLCanvasElement): void {
-        setImmediate(() => {
+        setTimeout(() => {
             this.setIconSrc(canvas.toDataURL("image/png"));
-        });
+        }, 0);
     }
 
     private setIconSrc(url: string): void {

src/vector/index.ts

@@ -25,9 +25,6 @@ import { extractErrorMessageFromError } from "matrix-react-sdk/src/components/vi
 import { parseQsFromFragment } from "./url_utils";
 import "./modernizr";
 
-// Make setImmediate available in bundle
-import "setimmediate";
-
 // Require common CSS here; this will make webpack process it into bundle.css.
 // Our own CSS (which is themed) is imported via separate webpack entry points
 // in webpack.config.js