LU-17509 dkms: SUSE15 depends on unavailable libmount

LU-17509 dkms: SUSE15 depends on unavailable libmount

SUSE renamed libmount in to libmount1 however the requiement
is statisifed by libmount-devel which in turn requires the
appropriate libmount package.

Drop the explicit libmount requirement from lustre-dkms.spec

Test-Parameters: trivial
HPE-bug-id: LUS-12141
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: Ifdee172483b73f9f66eb97883851febf94134309
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53945
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Neil Brown <neilb@suse.de>