refactor: Use variables directly in formatted strings (#7284)

made with `cargo clippy --all --fix` then manually reviewed to ensure
this was the only thing that changed.

deltachat-repl/src/main.rs

@@ -466,7 +466,7 @@ async fn handle_cmd(
                     println!("QR code svg written to: {file:#?}");
                 }
                 Err(err) => {
-                    bail!("Failed to get QR code svg: {}", err);
+                    bail!("Failed to get QR code svg: {err}");
                 }
             }
         }