[FIX] mail: "Invalid Date" errors on iOS Safari

Before this commit:
JS errors on iOS with Safari's browser due to the date syntax not being
supported:
```js
new Date("2023-08-18 14:02:53")
-> Invalid Date
```
This does prevent Odoo's backend to start up on the browser and the app
on iOS devices.

opw-3465337

closes odoo/odoo#132461

X-original-commit: a39391d0df644fce86f435ba3f39e7634d8e5172
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/core/common/thread_model.js

@@ -3,6 +3,7 @@
 import { ScrollPosition } from "@mail/core/common/scroll_position_model";
 import { createLocalId } from "@mail/utils/common/misc";
 
+import { deserializeDateTime } from "@web/core/l10n/dates";
 import { _t } from "@web/core/l10n/translation";
 import { Deferred } from "@web/core/utils/concurrency";
 
@@ -430,7 +431,7 @@ export class Thread {
         if (!this.last_interest_dt) {
             return undefined;
         }
-        return luxon.DateTime.fromISO(new Date(this.last_interest_dt).toISOString());
+        return deserializeDateTime(this.last_interest_dt);
     }
 
     /**