a few fix for kandinsky combined pipeline (#4352)
* add xformer
* enable_sequential_cpu_offload
* style
* Update src/diffusers/pipelines/kandinsky/pipeline_kandinsky_combined.py
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
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Co-authored-by: yiyixuxu <yixu310@gmail,com>
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
