sysutils/s6: update to 2.7.2.0

• Change maintainership
• Reorder some variables

Change log: http://www.skarnet.org/software/s6/upgrade.html

PR: 231159
Submitted by: colin-ports@heliocat.net
Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D17224