Whisper remove forced_decoder_ids for longform generation

[zucchini-nlp]

What does this PR do?

Fixes #29287 . As I wrote in the comments to the issue, the error is related to using forced-decoder-ids processor in longform generation, which suppresses all logits to -inf.

i see that forced-decoder-ids will be deprecated, but setting it to None will work for now.

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@sanchit-gandhi @ArthurZucker

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[sanchit-gandhi]

Good for me as a quick fix - thanks @zucchini-nlp! I'll open a PR to properly deprecate forced decoder ids as well

[sanchit-gandhi]

I made the full updates in #29485 - feel free to take a look