Because we have too many which are never used and I don't want to document
them.
1. Remove unused anchor_onchain_wait. When implemented, it should be
hardcoded to 100 or more.
2. Remove anchor_confirms_max. 10 always reasonable, and we can readd
an override option should someone need it.
3. max_htlc_expiry should be the same as locktime_max (which increases
from 3 to 5 days by default): they're both a limit on how long
funds can be locked up.
4. channel_update_interval should always be a dev option.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
edf1b3cec9