convert : ignore non-language tensors for Gemma4Model (#22753)

convert : ignore non-language tensors for Gemma4Model (#22753)

* convert : ignore non-language tensors for Gemma4Model

This commit adds a check to make sure only text language tensors are
handled in filter_tensors.

The motivation is that currently when trying to convert a Gemma4 model
the following error occurs:
```console
(venv) $ ./convert-gemma.sh
INFO:hf-to-gguf:Loading model: gemma-4-E2B-it
INFO:hf-to-gguf:Model architecture: Gemma4ForConditionalGeneration
INFO:hf-to-gguf:gguf: indexing model part 'model.safetensors'
INFO:gguf.gguf_writer:gguf: This GGUF file is for Little Endian only
INFO:hf-to-gguf:Exporting model...
INFO:hf-to-gguf:rope_freqs.weight,                 torch.float32 --> F32, shape = {256}
Traceback (most recent call last):
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 13752, in <module>
    main()
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 13746, in main
    model_instance.write()
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 945, in write
    self.prepare_tensors()
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 805, in prepare_tensors
    for new_name, data_torch in (self.modify_tensors(data_torch, name, bid)):
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 7925, in modify_tensors
    yield from super().modify_tensors(data_torch, name, bid)
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 7290, in modify_tensors
    yield from super().modify_tensors(data_torch, name, bid)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 579, in modify_tensors
    new_name = self.map_tensor_name(name)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/danbev/work/llama.cpp/./convert_hf_to_gguf.py", line 572, in map_tensor_name
    raise ValueError(f"Can not map tensor {name!r}")
ValueError: Can not map tensor 'model.embed_vision.embedding_projection.weight'
```

* add forgotten embed_vision and embed_audio

* improve

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Co-authored-by: Sigbjørn Skjæret <redacted>