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.

src/param.rs

@@ -284,7 +284,7 @@ impl str::FromStr for Params {
                     inner.insert(key, value);
                 }
             } else {
-                bail!("Not a key-value pair: {:?}", line);
+                bail!("Not a key-value pair: {line:?}");
             }
         }