devfs.rules: Do not expose "log" in the default devfs rules.

/etc/rc.d/jail no longer creates /dev/log as a symbolic link since
commit 84b354cb9ab61224713c159b1484e8f070fd37be.

PR: 228351
Reviewed by: jamie, mark
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D34563