LU-5710 build: fix typo suggesting openssl-devel requirement

LU-5710 build: fix typo suggesting openssl-devel requirement

Building without openssl-devel always prints a message suggesting to
install openssk-devel, which doesn't even exist. Fix typo.

Test-Parameters: trivial
Signed-off-by: Dominique Martinet <dominique.martinet@cea.fr>
Change-Id: Id99b9d4dff7ed95aba30e4929a984878a7d13f0a
Reviewed-on: https://review.whamcloud.com/37564
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sebastien Buisson <sbuisson@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>