Originally added in [1], and iwd added StateDirectory to its services
in [2] -- 4 days later.
("StateDirectory wasn't used when tmpfile snippet was added to NixOS")
(nevermind git -> release delay)
[1] 6e54e9253a
[2] upstream iwd git rev: 71ae0bee9c6320dae0083ed8c1700bc8fff1defb