Fix wrong param types, docs, and handles noise=None in scale_noise of FlowMatching schedulers

[Promisery]

What does this PR do?

In the scale_noise functions of all flow matching schedulers, the definitions and docs are wrong:

• timestep should be a torch.FloatTensor, not a float or int
• noise is not included in the document

Also, noise=None is not handled in the functions

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