models: clean up some dead switch branches in old models

[iggy]

Overview

Some of these if statements were copypastaed in a former refactor and never cleaned up to remove the cases that could never happen anymore. The only thing that's shared between these relatives anymore is llama_model_bert::graph::graph, so the rest of the code doesn't need the conditionals.

Additional information

I was looking into something unrelated and stumbled on this bit of dead code

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: YES — the issue was found and code change was implemented with AI assistance and manually reviewed and tested by me (full ./ci/run.sh passed)

[iggy]

I did write the commit message and PR description myself. The only thing I copied from my robit was the llama_model_bert::graph::graph bit.

[CISC]

You can also remove the moe_every_n_layers ffn block for all but nomic-bert-moe.

[iggy]

Fixed review feedback. Reran ci/run.sh ( ✔️ ). Also ran some standalone tests against the models this touches.

  ┌──────────────────────────┬────────────────┬────────────┬───────────┬────────────┐
  │          model           │      arch      │ embeddings │ load log  │ type label │
  ├──────────────────────────┼────────────────┼────────────┼───────────┼────────────┤
  │ bge-small-en-v1.5        │ bert           │ identical  │ -         │ -          │
  ├──────────────────────────┼────────────────┼────────────┼───────────┼────────────┤
  │ jina-reranker-v1-tiny-en │ jina-bert-v2   │ identical  │ -         │ -          │
  ├──────────────────────────┼────────────────┼────────────┼───────────┼────────────┤
  │ nomic-embed-text-v1.5    │ nomic-bert     │ identical  │ identical │ 137M       │
  ├──────────────────────────┼────────────────┼────────────┼───────────┼────────────┤
  │ nomic-embed-text-v2-moe  │ nomic-bert-moe │ identical  │ identical │ 475M       │
  ├──────────────────────────┼────────────────┼────────────┼───────────┼────────────┤
  │ jina-embeddings-v3       │ jina-bert-v3   │ identical  │ identical │ 558M       │
  └──────────────────────────┴────────────────┴────────────┴───────────┴────────────┘