netfilter: update MAINTAINERS

It's been a while since Patrick has been suspended as coreteam member [1].
Update this file to remove him.

While at this, remove references to all foo-tables variants, given the
project hosts more than just that, eg. ipset, conntrack, ...

[1] https://marc.info/?l=netfilter-devel&m=146887464512702



Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>