Missing Transformers initializer for Falcon models

[martin-gorner]

Repro code:
model5 = keras_hub.models.CausalLM.from_preset("hf://tiiuae/falcon-7b-instruct", dtype="bfloat16")
Result:
ValueError: KerasHub has no converter for huggingface/transformers models with model type 'falcon'

Now that the Falcon model family exists in Keras-hub, this should work.