I don't believe it can be deleted. However, you can grab the entire "iCloud" section of choices and drag it down as far as you can in the side bar to somewhat get it out of your way.
I see that you have it in "Favorites." I "think" this is only an alias to point to the same Pages folder as the one shown in iCloud. You can click & hold on the one in Favorites and drag it back to the iCloud section. If you drag it back to iCloud and then click the close icon to the right of iCloud, it will close and make it seem like it is "gone" (but actually just hidden)...
There will still be a "row" or entry that shows the word iCloud but you won't see Pages (folder) anymore, unless you click that same arrow to show what is accessible within that iCloud section again.