name claims guide should mention that DNSSEC proof is only method now

[pinheadmz]

Before mainnet launched, some trademark owners claimed their name through the founders' team and submitted mainnet addresses for those names to be automatically delivered: https://github.com/handshake-org/hs-names/blob/master/names/trademarks.json

These participants may still expect those addresses to "do something" -- they wont ;-)

[brandondees]

relevant list: https://github.com/handshake-org/hs-names/blob/master/names/trademarks.json