Removed 'platform' line from example ini; this kvp no longer used.

Removed note re 'platform' line from readme.txt
Some of you were using this feature (as intended) to advertise that the
client was running on some other/fake/amusing BBS package and OS.  I'm
told that this is not okay and may break things in the future.  (If you
update mrc-connector.js, the fact that you're running Synchronet and on
Linux or Windows i386, i686, x86_64 will be shared with the MRC server.)