fix DAC slow test

[kamilakesbi]

What does this PR do?

This PR aims to fix the slow test test_integration_24khz in DAC, recently added with PR #31494.

[HuggingFaceDocBuilderDev]

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[amyeroberts]

@kamilakesbi To run the slow model tests, you need to add the run-slow label to the PR. The order has to be label, then commit, so you'll need to push a [run_slow] commit again

[amyeroberts]

@kamilakesbi To run the slow tests for this model, you need to pass the model name in the commit message i.e. [run_slow] dac

[ylacombe]

Hey @kamilakesbi, many thanks for opening this PR!
Do you think you'll be able to finish it? If not, it would be of a tremendous help if you could provide a simple snippet on the original DAC library so that I can take a look myself!

[ylacombe]

supersede by #34088