[APPS-1082][INT] Move translation titles to JSON

:koala: :+1:

This PR moves translation titles into en.json and therefore allows us to remove the translation YAML file.

__BLOCKED BY:__ https://github.com/zendesk/zendesk_app_market/pull/545 being deployed to production.

### RELATED
- [ZAM PR](https://github.com/zendesk/zendesk_app_market/pull/545)
- [JIRA](https://zendesk.atlassian.net/browse/APPS-1082)

/cc @zendesk/quokka @pelletier