Remove token-adding chat embedding params

[noamgat]

This follows the discussion in:

#10501 (comment)

Where @DarkLight1337 agreed that its better to remove the parameters altogether.

In embedding, the model does not generate additional tokens on top of the input text. Therefore, all parameters like "should a start-of-assistant-turn token be added" don't make sense, and should be removed.

This replaces that PR with the agreed-upon solution

[github-actions]

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[noamgat]

Hey, some of the tests fail but it looks unrelated to my changes. How can we proceed with the merge?

[DarkLight1337]

Asking for force-merge.