This is redundant if it's a public channel, but vital if it's not. Publishing unconditionally makes
it easier for gossmap: we create a local modification all the time, even if redundant (and we can
have the actual capacity ceiling accurate in this case, since we know it for local channels).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `listpeerchannels` now shows gossip update contents (even if channel unannounced).