Unix CM: Fix bogus character in license string

A stray $ had crept into the license string in afs_dcache.c. Fix it.

Reviewed-on: http://gerrit.openafs.org/9233
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
(cherry picked from commit 983d67616b670c5d57c8c67578fdb52f2bb3ddbd)

Change-Id: I21d31dc9e50e6be253cc7e7878e1079567f10220
Reviewed-on: http://gerrit.openafs.org/9529
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>