Fix broken rustdoc link in InvoicePayer

Author: jkczyz

lightning-invoice/src/payment.rs

@@ -134,7 +134,7 @@ use std::ops::Deref;
 use std::sync::Mutex;
 use std::time::{Duration, SystemTime};
 
-/// A utility for paying [`Invoice]`s.
+/// A utility for paying [`Invoice`]s.
 pub struct InvoicePayer<P: Deref, R, S: Deref, L: Deref, E>
 where
 	P::Target: Payer,