Refine hold/certification DenyGroup banner message

Currently both of them is just two lines of message. Might be better to make it more obvious like MOTD kinda to block? or Notice block to make the message stand out.

Currently in production, which is maintained here https://gitlab.rc.uab.edu/rc/ansible-vars/-/blob/main/prod#L171:

hold:

Your account is currently on hold.
Please contact Research Computing at support@listserv.uab.edu to resolve this issue.

certification:

Your annual account certification is overdue.
Please visit https://rc.uab.edu/account to complete your certification and resume using your account.