samples: hello_world: Run cargo fmt

Format the source according to the default rules. This provides a
baseline for future changes to require well-formatted source.

Signed-off-by: David Brown <[email protected]>

Author: d3zd3z

samples/hello_world/src/lib.rs

@@ -7,7 +7,9 @@ use log::info;
 
 #[no_mangle]
 extern "C" fn rust_main() {
-    unsafe { zephyr::set_logger().unwrap(); }
+    unsafe {
+        zephyr::set_logger().unwrap();
+    }
 
     info!("Hello world from Rust on {}", zephyr::kconfig::CONFIG_BOARD);
 }