net/chrony: update to 4.8

Changelog: https://chrony-project.org/news.html#_27_aug_2025_chrony_4_8_released

While here, disable the socket.c self-test, which fails because the test
sets a TCP accept()ed socket O_NONBLOCK and recvmsg() returns error
with errno==EAGAIN, unless run under truss.

Upstream bug report via mailing list, see:
https://www.mail-archive.com/chrony-users@chrony.tuxfamily.org/msg03849.html