add the xm.mark_step for the first denosing loop (#10530)
* Update rerender_a_video.py
* Update rerender_a_video.py
* Update examples/community/rerender_a_video.py
Co-authored-by: hlky <hlky@hlky.ac>
* Update rerender_a_video.py
* make style
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Co-authored-by: hlky <hlky@hlky.ac>
Co-authored-by: YiYi Xu <yixu310@gmail.com>
