net_processing: drop 8 headers threshold for incoming BIP130

Summary:
With the Misbehavior score gone for non-connecting headers (see previous
commit), there is no need to only treat headers messages with up to 8
headers as potential BIP130 announcements. BIP130 does not specify such
a limit; it was purely a heuristic.

This is a partial backport of core#29575
https://github.com/bitcoin/bitcoin/pull/29575/commits/5120ab1478c200b18ee621a6ffa0362f4e991959

Depends on D18030

Test Plan: ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D18031