net/wifibox: Update to 0.8.2

• Update image to Alpine Linux 3.15.4: https://alpinelinux.org/posts/Alpine-3.12.12-3.13.10-3.14.6-3.15.4-released.html

Changes: https://github.com/pgj/freebsd-wifibox/releases/tag/0.8.2
MFH: 2022Q2 (due to a security update in the image)
(cherry picked from commit 4efb1595f8a5b9122ebfc9d5fd40096d2d41e85c)