Transifex API version used by i18n script is deprecated

The API [v2](https://docs.transifex.com/api/introduction) endpoints used by the i18n scripts to push and pull translations from Transifex are deprecated, we must migrate to [v3](https://transifex.github.io/openapi/index.html#section/Introduction).

For reference this is the i18n tool that calls the API: https://github.com/arduino/arduino-cli/tree/master/i18n