[`Docs`] Fix typos and update files at API's Pipelines page 2 (#5748)
* Fix typos, update, add Copyright info, and trim trailing whitespace
* Update docs/source/en/api/pipelines/text_to_video_zero.md
Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>
* 1 second is not a long video, but 6 seconds is
* Update text_to_video_zero.md
* Update text_to_video_zero.md
* Update text_to_video_zero.md
* Update wuerstchen.md
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Co-authored-by: Steven Liu <59462357+stevhliu@users.noreply.github.com>