Fixup: add missing trailing newline

Author: LeSeulArtichaut

src/test/ui/rfcs/rfc-2396-target_feature-11/closures-inherit-target_feature.rs

@@ -15,4 +15,4 @@ fn use_avx() -> Box<dyn Fn()> {
     Box::new(|| also_use_avx())
 }
 
-fn main() {}
+fn main() {}