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, markj
Differential Revision: https://reviews.freebsd.org/D34563

(cherry picked from commit 2670ea8a075ea29a0eee9d227c4cdf585a7b3b55)
(cherry picked from commit 02fe4484379c1e67c22ad6abbeea10c8a20d10eb)