mail/fetchmail: update to 6.6.0, SMTP TLS support

Changelog: https://gitlab.com/fetchmail/fetchmail/-/blob/6.6.0/NEWS?ref_type=tags#L110

PR: 209617
MFH: 2025Q4
Approved by: Corey Halpin (maintainer)

(cherry picked from commit 4d4259b9d667a10f6a1fc811bfe68bb5a69bcfa9)