Changing the text of "Subscribed Successfully" for single opt-in

I want to use a custom message in place of “Subscribed Successfully” message shown in the widget for single opt-in.

I have tried changing the text using “Loco Translate”. However, despite updating the pot file, text stays the same.

Alternate is to modify the JS file to hard code the desired text, but that’s futile as any changes will be overwritten by an update.

Please let me know what can be done for this?

https://www.ads-software.com/plugins/email-subscribers/