afs: remove dead code afs_osi_SetTime

afs: remove dead code afs_osi_SetTime

afs_osi_SetTime() has been dead code since -settime support was removed
with commit 1d9888be486198868983048eeffabdfef5afa94b 'Remove
-settime/RXAFS_GetTime client support'.

Remove the dead code.

No functional change is incurred by this commit.

Reviewed-on: https://gerrit.openafs.org/13393
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 16b981ec6697b511c36c09adfeb8b79eaf2345b0)

Change-Id: I3fa92cbe1598703b4eddd78e4c7afdc04c525750
Reviewed-on: https://gerrit.openafs.org/13407
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>