www/squid: Update 7.4 => 7.6
Changelogs:
https://github.com/squid-cache/squid/blob/SQUID_7_6/ChangeLog
PR: 296633
Approved by: Pavel Timofeev <timp87@gmail.com> (maintainer)
Sponsored by: UNIS Labs
Co-authored-by: takefu@airport.fm
MFH: 2026Q3
(cherry picked from commit b7c3610b959d1b5158c3c49db6ca69a3f15a15fa)