docs: var/local -> var/usrlocal
docs: var/local -> var/usrlocal

Signed-off-by: Arnaud Rebillout <arnaud.rebillout@collabora.com>

Closes: #1588
Approved by: jlebon

GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree,GNOME/ostree