feat: Replace alertMixin usage with useAlert (#9793)

# Pull Request Template

## Description

This PR will replace the usage of `alertMixin` from the code base with
the `useAlert` composable.

Fixes
https://linear.app/chatwoot/issue/CW-3462/replace-alertmixin-usage-with-usealert

## Type of change

- [x] Breaking change (fix or feature that would cause existing
functionality not to work as expected)

## How Has This Been Tested?

Please refer this issue description

https://linear.app/chatwoot/issue/CW-3462/replace-alertmixin-usage-with-usealert


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] 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/mixins/aiMixin.js

@@ -1,10 +1,9 @@
 import { mapGetters } from 'vuex';
+import { useAlert } from 'dashboard/composables';
 import { OPEN_AI_EVENTS } from '../helper/AnalyticsHelper/events';
 import OpenAPI from '../api/integrations/openapi';
-import alertMixin from 'shared/mixins/alertMixin';
 
 export default {
-  mixins: [alertMixin],
   mounted() {
     this.fetchIntegrationsIfRequired();
   },
@@ -101,7 +100,7 @@ export default {
         } = result;
         return generatedMessage;
       } catch (error) {
-        this.showAlert(this.$t('INTEGRATION_SETTINGS.OPEN_AI.GENERATE_ERROR'));
+        useAlert(this.$t('INTEGRATION_SETTINGS.OPEN_AI.GENERATE_ERROR'));
         return '';
       }
     },