[FIX] im_livechat: font face set not iterable

This commit fixes a traceback that occurs on the frontend
on firefox only. The issue is that the `FontFaceSet.values()`
return value is considered as non iterable while it is an iterator.

This commit solves this issue by using directly `document.fonts`
which is considered an iterator even by firefox.

closes odoo/odoo#123672

See: https://bugzilla.mozilla.org/show_bug.cgi?id=1780657
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/im_livechat/static/src/embed/boot_helpers.js

@@ -4,7 +4,7 @@ import { serverUrl } from "@im_livechat/embed/livechat_data";
 
 async function loadFontAwesome() {
     await document.fonts.ready;
-    if ([...document.fonts.values()].some(({ family }) => family === "FontAwesome")) {
+    if ([...document.fonts].some(({ family }) => family === "FontAwesome")) {
         // FontAwesome already loaded.
         return;
     }