The *schemas* were added in v24.05, but the actual fields are much older. Unfortunately,
fixing this required a manual edit of the .msggen.json file, as msggen won't let the
added version change (for good reason).
Versions when these notifications were originally added:
connect: v0.6.3
channel_opened: v0.7.2.1:
channel_state_changed: v0.9.1
channel_open_failed: v0.9.3
block_added: v22.11
custommsg: v24.02
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
