fixed formatting issue

Author: DanielLacina

src/cluster/agglomerative.rs

@@ -97,7 +97,9 @@ impl<TX: Number, TY: Number, X: Array2<TX>, Y: Array1<TY>> AgglomerativeClusteri
         if n_clusters > num_samples {
             return Err(Failed::because(
                 FailedError::ParametersError,
-                &format!("n_clusters: {n_clusters} cannot be greater than n_samples: {num_samples}"),
+                &format!(
++                    "n_clusters: {n_clusters} cannot be greater than n_samples: {num_samples}"
++                ),
             ));
         }