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 939fd450)