Implement Clippy suggestions

They were actually sensible for once???

src/persist/sqlite_manager.rs

@@ -99,7 +99,7 @@ async fn create_client(data_dir: &OsStr) -> Result<Client, DataManagerError> {
           Ok(())
         })
         .await
-        .map(|_| client)
+        .map(|()| client)
     })
     .await;