Fix spelling of `synthetic` (#613)

events.go

@@ -10,15 +10,15 @@ import (
 //go:generate go run tools/cmd/eventhandlers/main.go
 
 // Connect is the data for a Connect event.
-// This is a sythetic event and is not dispatched by Discord.
+// This is a synthetic event and is not dispatched by Discord.
 type Connect struct{}
 
 // Disconnect is the data for a Disconnect event.
-// This is a sythetic event and is not dispatched by Discord.
+// This is a synthetic event and is not dispatched by Discord.
 type Disconnect struct{}
 
 // RateLimit is the data for a RateLimit event.
-// This is a sythetic event and is not dispatched by Discord.
+// This is a synthetic event and is not dispatched by Discord.
 type RateLimit struct {
 	*TooManyRequests
 	URL string