Check channel type features are consistent

When reading ChannelTransactionParameters, the channel_type_features
defaults to only_static_remote_key. This is similarly the case for
reading a channel. Instead of overriding the latter with the former,
check that they are consistent. It doesn't appear that overriding was
ever necessary.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -10879,9 +10879,9 @@ impl<'a, 'b, 'c, ES: Deref, SP: Deref> ReadableArgs<(&'a ES, &'b SP, &'c Channel
 			return Err(DecodeError::UnknownRequiredFeature);
 		}
 
-		// ChannelTransactionParameters may have had an empty features set upon deserialization.
-		// To account for that, we're proactively setting/overriding the field here.
-		channel_parameters.channel_type_features = chan_features;
+		if chan_features != channel_parameters.channel_type_features {
+			return Err(DecodeError::InvalidValue);
+		}
 
 		let mut secp_ctx = Secp256k1::new();
 		secp_ctx.seeded_randomize(&entropy_source.get_secure_random_bytes());