Add missing comma to cfg_attr for rmt-legacy (#559)

Author: z-jxy

src/lib.rs

@@ -99,7 +99,7 @@ pub mod reset;
 pub mod rmt;
 #[cfg(feature = "rmt-legacy")]
 #[cfg_attr(
-    feature = "rmt-legacy"
+    feature = "rmt-legacy",
     deprecated(
         since = "0.46.0",
         note = "use the new `rmt` api by disabling the `rmt-legacy` feature"