Wuerstchen fixes (#4942)
* fix arguments and make example code work
* change arguments in combined test
* Add default timesteps
* style
* fixed test
* fix broken test
* formatting
* fix docstrings
* fix num_images_per_prompt
* fix doc styles
* please dont change this
* fix tests
* rename to DEFAULT_STAGE_C_TIMESTEPS
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Co-authored-by: Dominic Rampas <d6582533@gmail.com>
