Fix typo in cogvideo pipeline

[lichenyu20]

What does this PR do?

Fixed typos in pipeline_cogvideox_image2video.py and pipeline_cogvideox.py.
The default fps is 8. You can refer to official implementation of cogvideo repo.

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Who can review?

@yiyixuxu
@asomoza
@stevhliu
@sayakpaul

[a-r-r-o-w]

Thanks!

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