www/moin2: update to 2.0.0b3 and take maintainership

Changelog:

• https://github.com/moinwiki/moin/releases/tag/2.0.0b1
• https://github.com/moinwiki/moin/releases/tag/2.0.0b2
• https://github.com/moinwiki/moin/releases/tag/2.0.0b3

PR: 287621
Reported by: Krzysztof <ports@bsdserwis.com> (new maintainer)