fix typo in prometheus_metrics_example (#2627)

Signed-off-by: Vigith Maurice <[email protected]>

examples/prometheus-metrics/src/main.rs

@@ -64,7 +64,7 @@ async fn main() {
     tracing_subscriber::registry()
         .with(
             tracing_subscriber::EnvFilter::try_from_default_env()
-                .unwrap_or_else(|_| "example_todos=debug,tower_http=debug".into()),
+                .unwrap_or_else(|_| "example_prometheus_metrics=debug,tower_http=debug".into()),
         )
         .with(tracing_subscriber::fmt::layer())
         .init();