Switch 'match' to 'if let' in main.rs::after

This lets us drop a level of indentation, and remove the clunky match arm for Ok(()) => ()

:)

src/main.rs

@@ -91,9 +91,7 @@ async fn dispatch_error(ctx: &Context, msg: &Message, error: DispatchError) {
 #[hook]
 async fn after(ctx: &Context, msg: &Message, command_name: &str, command_result: CommandResult) {
     // prints error in chat
-    match command_result {
-        Ok(()) => (),
-        Err(why) => {
+    if let Err(why) = command_result {
         let _ = msg
             .channel_id
             .send_message(&ctx.http, |m| {
@@ -115,7 +113,6 @@ async fn after(ctx: &Context, msg: &Message, command_name: &str, command_result:
             )
         );
     }
-    }
 }
 
 #[group]