Model adaptation is now available for latest_long models in 13 languages

## Feature [Model adaptation](https://cloud.google.com/speech-to-text/docs/adaptation-model) is now available for `latest_long` models in 13 languages. Also, its quality was substantially improved for `latest_short` models. To determine whether this feature is available for your language, see [Language support](https://cloud.google.com/speech-to-text/docs/speech-to-text-supported-languages).