multi: fix a variety of typos throughout the repo

routing/pathfind.go

@@ -30,7 +30,7 @@ type Route struct {
 	// route. This is the CLTV value that should be extended to the first
 	// hop in the route. All other hops will decrement the time-lock as
 	// advertised, leaving enough time for all hops to wait for or present
-	// the payment pre-image to complete the payment.
+	// the payment preimage to complete the payment.
 	TotalTimeLock uint32
 
 	// TotalFees is the sum of the fees paid at each hop within the final

routing/router.go

@@ -609,7 +609,7 @@ func (r *ChannelRouter) processNetworkAnnouncement(msg lnwire.Message) bool {
 	return true
 }
 
-// syncRequest represents a request from an outside sub-system to the wallet to
+// syncRequest represents a request from an outside subsystem to the wallet to
 // sync a new node to the latest graph state.
 type syncRequest struct {
 	node *btcec.PublicKey