luci-app-nut: Remove old no-op uci-defaults script

Remove old uci-defaults script that was supposed to be run
if nut was older than 2.4.7-8. Nut has been at 2.7.4-9 or newer
since 2018.

(Ps. The script had faulty logic: the version check never matched.)

Fixes #6966

Signed-off-by: Hannu Nyman <hannu.nyman@iki.fi>