[Frontend] [Minor] Fix tqdm progress bar for n > 1

[franzscherr]

When generating multiple outputs for single prompts (n > 1) the tqdm progress bar provides incorrect progress (#11519).

This pull request updates the progress bar by the number of generated responses as the total requests consider n.

Fixes #11519

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[njhill]

Thanks @franzscherr

[njhill]

Actually there is already a PR for this and a comment there which should be addressed #12428. Specifically we want to make sure this ends up being correct with both the V0 and V1 implementations - see #10980 cc @afeldman-nm.