feat: Move timeMixin to a helper (#9799)

# Pull Request Template

## Description

This PR will replace the usage of `timeMixin` with `timeHelper`

Fixes
https://linear.app/chatwoot/issue/CW-3451/move-time-mixin-to-a-helper

## Type of change

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

## How Has This Been Tested?

Please refer to this issue description.
https://linear.app/chatwoot/issue/CW-3451/move-time-mixin-to-a-helper

## 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
- [ ] 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
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/javascript/dashboard/components/ChatList.vue

@@ -122,7 +122,6 @@ import ChatListHeader from './ChatListHeader.vue';
 import ConversationAdvancedFilter from './widgets/conversation/ConversationAdvancedFilter.vue';
 import ChatTypeTabs from './widgets/ChatTypeTabs.vue';
 import ConversationItem from './ConversationItem.vue';
-import timeMixin from '../mixins/time';
 import keyboardEventListenerMixins from 'shared/mixins/keyboardEventListenerMixins';
 import conversationMixin from '../mixins/conversations';
 import wootConstants from 'dashboard/constants/globals';
@@ -159,7 +158,6 @@ export default {
     VirtualList,
   },
   mixins: [
-    timeMixin,
     conversationMixin,
     keyboardEventListenerMixins,
     alertMixin,