f - fix create_refund_builder docs

Author: jkczyz

lightning/src/ln/channelmanager.rs

@@ -7110,8 +7110,8 @@ where
 
 	/// Creates a [`RefundBuilder`] such that the [`Refund`] it builds is recognized by the
 	/// [`ChannelManager`] when handling [`Bolt12Invoice`] messages for the refund. The builder will
-	/// have an expiration set, if provided. Any changes to the expiration on the returned builder
-	/// will not be honored by [`ChannelManager`].
+	/// have the provided expiration set. Any changes to the expiration on the returned builder will
+	/// not be honored by [`ChannelManager`].
 	///
 	/// The provided `payment_id` is used to ensure that only one invoice is paid for the refund.
 	///