Add missing inbound_payment_id_secret write in ChannelManager

In aa09c33 we added a new secret
in `ChannelManager` with which to derive inbound `PaymentId`s. We
added read support for the new field, but forgot to add writing
support for it. Here we fix this oversight.

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -12024,6 +12024,7 @@ where
 			(11, self.probing_cookie_secret, required),
 			(13, htlc_onion_fields, optional_vec),
 			(14, decode_update_add_htlcs_opt, option),
+			(15, self.inbound_payment_id_secret, required),
 		});
 
 		Ok(())