Description:

XFER to newer backends now assumes at least the current mailbox version,
rather than the oldest supported mailbox version.


Config changes:

None


Upgrade instructions:

This is the future absence of an upgrade instruction: a server containing
this change no longer needs to be upgraded to a version that specifically
recognises newer backends prior to XFERing mailboxes to them.


GitHub issue:

https://github.com/cyrusimap/cyrus-imapd/issues/4380
