[Checkins] [zopefoundation/Zope] c99111: - add link to requires.io [ci skip]

[Jens Vagelpohl]

  Branch: refs/heads/4.x
  Home:   https://github.com/zopefoundation/Zope
  Commit: c99111c6f653f0615e53d646afa134f9bac1c973
      https://github.com/zopefoundation/Zope/commit/c99111c6f653f0615e53d646afa134f9bac1c973
  Author: Jens Vagelpohl <jens at netz.ooo>
  Date:   2019-11-27 (Wed, 27 Nov 2019)

  Changed paths:
    M docs/maintenance.rst

  Log Message:
  -----------
  - add link to requires.io [ci skip]