bsd-family-tree: Add NetBSD 9.2

NetBSD 9.2 was released on May 12, 2021

Submitted by: Martin Husemann
Sponsored by: Netflix
Approved by: re@ (delphij@)

(cherry picked from commit 71a071be1c5ae971421a830d76ee30186ffdd199)
(cherry picked from commit 127f5e8969b12e8f96921d26f08b0f060cf9a254)