The link provided by Akash might not apply to this question, because the link is about images provided through an “integrated search feature.” But the sky replacement files are bundled with the software.
However, this question was answered in another thread. See the comment at this link:
Sky Presets may be used in commercial work just like stock images and shapes/brushes. You just are not allowed to bundle and resell them.
In other words you can sell works that you make with the bundled sky images, just don’t resell the unmodified Adobe sky images themselves.