[charms] Proposing Brian Haley and Nicolas Bock for OpenStack Charms core

Hi everyone, I would like to propose Brian Haley and Nicolas Bock for the OpenStack Charms core development team. Both Brian and Nicolas have been members of the stable charms core team since 2023 and been hugely helpful in that role, providing insightful feedback to reviews as well as contributions of their own. Nicolas has also been a contributor to the OpenStack charms for many years and Brian is well versed in the ways of upstream OpenStack maintenance through his role as Neutron PTL so I have full confidence that they will prove valuable additions to the charms-core team. Thank you both for your contributions to the project! Regards, Ed