extensions_ct2n: Add dependency in scp2/InstallModule_extensions.mk

9df0e4a709735e5fb5c0e87779b0694c512f0de7 moved ct2n to AutoInstall,
but missed to add dependency in  scp2/InstallModule_extensions.mk.

Change-Id: Ibfc30f1efa494996e832c8039fde69420f0ad5ee
Reviewed-on: https://gerrit.libreoffice.org/13398
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Tested-by: Michael Stahl <mstahl@redhat.com>