Nightly build problems.

[wxiaoguang]

Outdated "docs"

I think no one needs them, so they can be removed.

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Use "main-nightly" for consistency

I believe we should also call the container images as "main-nightly" but not only "nightly". At the moment, "nightly" can't help users to easily find the real main-nightly build they need.

[techknowlogick]

thanks. ive removed the outdated files from the s3 bucket. As for renaming the image name that's doable, and now that we use our own registry we can set up a redirect for people using the old tag name.