chore(rustfmt): use nightly (#2325)

Stable rustfmt lacks a lot of features resulting in worse formatted
code, thus use nightly formatter.

examples/util/tracing.rs

@@ -4,9 +4,7 @@ pub fn init() {
 
     tracing_subscriber::fmt()
         .with_env_filter(
-            EnvFilter::builder()
-                .with_default_directive(LevelFilter::INFO.into())
-                .from_env_lossy(),
+            EnvFilter::builder().with_default_directive(LevelFilter::INFO.into()).from_env_lossy(),
         )
         .init();
 }