usergroups: Update venues for Hamburg and Portland

Hamburg changed venue after 30 years.
Include link to their meeting page and update venue to match.
Reported by cracauer@ on
https://forums.freebsd.org/threads/102512/#post-757478

Portland website has updated their meeting link.
Calagator search now quotes "BSD Pizza Night".
This removes false positives.

Reviewed by: ziaee
Signed-off-by: bigsneaky@duck.com
Closes: https://github.com/freebsd/freebsd-doc/pull/663