Update the reference for text_to_video.md (#5706)
* Update the reference for text_to_video.md
The original reference (VideoFusion) might be misleading. VideoFusion is not open-sourced. I am the co-first author of ModelScopeT2V. I change the referred paper to the right one.
* Update docs/source/en/api/pipelines/text_to_video.md
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
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Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
