style(clippy): enforce clippy use_self lint

Clippy's `use_self` line ensures that `Self` is used instead of the real
name whenever possible. This makes searching easier and cleans up the
code a bit.

src/mpris.rs

@@ -491,7 +491,7 @@ impl MprisManager {
             }
         });
 
-        MprisManager { tx }
+        Self { tx }
     }
 
     async fn serve(