mail/fetchmail: security update to 6.5.6

To fix https://www.fetchmail.info/fetchmail-SA-2025-01.txt

and the Error: Orphaned: %%PYTHON_SITELIBDIR%%/__pycache__/fetchmailconf%%PYTHON_TAG%%.opt-2.pyc
from

Approved by: Corey Halpin (maintainer)
PR: 289823
PR: 289979
Security: 21fba35e-a05f-11f0-a8b8-a1ef31191bc1
MFH: 2025Q4

(cherry picked from commit 939fd45010734c004fa5090549d399c45e44840e)