community/gajim: upgrade to 1.9.3 & community/py3-nbxmpp: upgrade to 5.0.3

• https://dev.gajim.org/gajim/gajim/-/blob/1.9.3/ChangeLog
• https://dev.gajim.org/gajim/python-nbxmpp/-/blob/5.0.3/ChangeLog