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11f527ac - Add `Karras sigmas` to HeunDiscreteScheduler (#3160)

Add `Karras sigmas` to HeunDiscreteScheduler (#3160) * Add karras pattern to discrete heun scheduler * Add integration test * Fix failing CI on pytorch test on M1 (mps) --------- Co-authored-by: Patrick von Platen <patrick.v.platen@gmail.com>