BentoML

Hello. I'm using BentoML with the Keras framework (trhough TensorFlow). When using it, I get this warning: `
```BentoMLDeprecationWarning: `bentoml.keras` is deprecated since v1.4 and will be removed in a future version.```
I couldn't find any information about Keras deprecation, and as far as I remember, this warning has been showing since Bento v1.3 a few months ago. Is Keras support going to be effectively removed?
For reference, Keras in BentoML doc: <https://docs.bentoml.com/en/latest/reference/bentoml/frameworks/keras.html> (without anything about deprecation)

The warning seems to have been added in <https://github.com/bentoml/BentoML/pull/5023>. It concerns a more general "Legacy API", but it is still not clear to me if Bento is going to remove Keras support or if these are simply going to be refactored in a new API.