Remove panic when inbound peer sends OpenChannelRequest with no type specified and node is manually accepting requests

[domZippilli]

This bit right here causes a panic if a correctly-formed message is sent to an LDK node that is manually accepting channel open requests:

https://github.com/lightningdevkit/rust-lightning/blob/15b7f667b05b09a25af8ab2791ea4f0752fcc2ab/lightning/src/ln/channelmanager.rs#L6184C2-L6184C2