Fix gguf loading via Transformers

[CL-ModelCloud]

No description provided.

[Qubitium]

@baberabb This PR contains simple fix so HF Transformers can properly load gguf models via the gguf_file parameter.

[Qubitium]

@baberabb During our testing, we found gguf tokenizer load will fail is you override default use_fast=True with use_fast=False + gguf_file enabled. We can conclude gguf format is not compatbile with use_fast and added code bypass.

[LSinev]

If I may suggest, please update the documentation (*.md files) with description of this new option and provide some examples of usage (from terminal, at least).