MAINTAINERS: remove Dave Watson as TLS maintainer

Dave's Facebook email address is not working, and my attempts
to contact him are failing. Let's remove it to trim down the
list of TLS maintainers.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>