Remove deprecated cbbackup and cbrestore guides from 7.0 and Neo docs

When you Google couchbase cbbackup, you tend to end up on the cbbackup "Guide" page, which does not say that cbbackup is deprecated.  

More relevant, however, is that the "Guide" pages for cbbackup and cbrestore should just be removed from 7.0 and Neo docs since cbbackup and cbrestore are deprecated, and we don't want people to start using them.   (The CLI Reference pages for cbbackup and cbrestore, which do say that they are deprecated, should be kept.)

Remove these – 7.0 and Neo versions of the cbbackup and cbrestore guide pages :

https://docs.couchbase.com/server/current/cli/cbtools/guides/cbbackup-guide.html

https://docs.couchbase.com/server/current/cli/cbtools/guides/cbrestore-guide.html

To reduce the foot print of cbrestore doc info in 7.0 and Neo, consider adding the below "rehash=1" info to the main CLI Reference page for cbrestore.   If the "rehash=1" page is to be kept as a separate link, make sure that it has the "(Deprecated)" label on the page.

https://docs.couchbase.com/server/current/cli/cbtools/guides/cbrestore-rehash1-guide.html