No functional change; the "restrict" key option is a shorthand for:
It was added in OpenSSH 7.2 (2016-02-29) as a convenient way to specify an authorized key should have "all current and future key restrictions" applied to it.
Also switch to a relative borg command since its location is not really
standardized; on rsync.net it appears to be located under usr/local/bin
(though /usr/bin/borg works too, even if it doesn't exist!) and Hetzner
just forces its own command, ignoring ours.
The Borg documentation seems to agree with both the above alterations: