Updated docs on PeerManager::process_events.

Try to make it a bit more clear that there are downsides to solely
relying on `lightning-net-tokio`, and it's still recommended to
occasionally call this function in a separate loop.

Author: mhrheaume

lightning/src/ln/peer_handler.rs

@@ -2057,8 +2057,12 @@ impl<Descriptor: SocketDescriptor, CM: Deref, RM: Deref, OM: Deref, L: Deref, CM
 	/// May call [`send_data`] on [`SocketDescriptor`]s. Thus, be very careful with reentrancy
 	/// issues!
 	///
-	/// You don't have to call this function explicitly if you are using [`lightning-net-tokio`]
-	/// or one of the other clients provided in our language bindings.
+	/// You're not required to call this function explicitly if you are using [`lightning-net-tokio`]
+	/// or one of the other clients provided in our language bindings, as it will be called
+	/// automatically when a message is received from a peer. However, it can in some cases delay
+	/// messages from going out if peers are not sending messages, so it is still recommended to
+	/// call it when messages may need to be sent, e.g. after processing channel events that may
+	/// have resulted in an update to the channel state.
 	///
 	/// Note that if there are any other calls to this function waiting on lock(s) this may return
 	/// without doing any work. All available events that need handling will be handled before the