convert : fix encoding of WPM vocab for BERT models (#18500)
* convert: avoid token collision when stripping ## prefix
* convert: use token types for BERT special tokens check
* Update convert_hf_to_gguf.py
Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>
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Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>