Allow specifying denoising_start and denoising_end as integers representing the discrete timesteps, fixing the XL ensemble not working for many schedulers (#4115)
* Fix the XL ensemble not working for any kerras scheduler sigmas and having an off by one bug
* Update src/diffusers/pipelines/stable_diffusion_xl/pipeline_stable_diffusion_xl.py
* make sytle
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Co-authored-by: Jimmy <39@🇺🇸.com>
Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>