newsyslog(8): Disable compression by default in newsyslog.conf.

Historically, newsyslog compressed rotated log files to save disk space.
This was helpful when storage was limited. However, with modern files
systems like ZFS providing built-in compression and with larger disks
now common, the benefits of additional log compression have diminished,
especially given the inconvenience of needing to decompress logs when
searching for specific patterns.

This change updates the default /etc/newsyslog.conf to specify:

<compress> none

disabling compression for new installations or default setups.
It does not modify the behavior of the newsyslog utility itself; users
can still enable compression as needed via configuration.

MFC: never
Reviewed by: zlei, dvl, otis
Relnotes: yes

Differential Revision: https://reviews.freebsd.org/D43169