Rename confusing var

src/main.rs

@@ -25,7 +25,7 @@ fn main() -> Result<(), Box<dyn Error>> {
     }
 
     let mut lb = listenbrainz::Client::new();
-    let mut drpc = Client::new(env::var("DISCORD_CLIENT_ID")?.parse()?);
+    let mut drpc = Client::new(env::var("DISCORD_APP_ID")?.parse()?);
     drpc.start();
 
     let mut cover_cache: HashMap<String, String> = HashMap::new();