main/busybox: fix wget headers

add header 'Accept: /' similar to what GNU wget and curl does.

This is needed for sites like https://netfilter.org

Discovered in !61665 (merged)

fixes: #15861 (closed)

ref: https://bugs.busybox.net/show_bug.cgi?id=15982 ref: http://lists.busybox.net/pipermail/busybox/2024-March/090661.html