things-manager: remove reference to groupsyncaction

things-manager: remove reference to groupsyncaction

This SConscript tried to include service/things-manager/sampleapp/linux
/groupsyncaction/SConscript which does not exists, remove the reference.

Change-Id: Ic5265db3757539113121d1e68df542ca744b54e8
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Reviewed-on: https://gerrit.iotivity.org/gerrit/4819
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jihun Ha <jihun.ha@samsung.com>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>