chore: update the voice call ringtone (#14636)

## Linear Ticket
https://linear.app/chatwoot/issue/CW-7260/update-the-voice-call-ringtone

## Description

Updates the incoming voice call ringtone. The dashboard call widget now
plays the new tone while an inbound call is unanswered, replacing the
previous bell sound.

## Type of change

- [x] New feature (non-breaking change which adds functionality)

## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [x] Any dependent changes have been merged and published in downstream
modules

app/javascript/dashboard/components-next/call/FloatingCallWidget.vue

@@ -12,7 +12,7 @@ import WindowVisibilityHelper from 'dashboard/helper/AudioAlerts/WindowVisibilit
 import CallCard from 'dashboard/components-next/call/CallCard.vue';
 import countriesList from 'shared/constants/countries.js';
 
-const RINGTONE_URL = '/audio/dashboard/bell.mp3';
+const RINGTONE_URL = '/audio/dashboard/ringtone.mp3';
 
 const route = useRoute();
 const router = useRouter();