linux24: remove unused NUMPAGGROUPS define

linux24: remove unused NUMPAGGROUPS define

Remove the unused NUMPAGGROUPS define in the pag group handling
implementation for linux24. PAGS always take two group ids in linux24,
so the NUMPAGGROUPS define was not used in linux24. Remove the unused
constant.

This is a 1.6.x only change, since linux24 support has been removed on
the master branch.

Change-Id: I10d4d5744420b075a10deecf052d2ecc128ad8fe
Reviewed-on: https://gerrit.openafs.org/12563
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>