fix(aggregation): GradDrop error message typo (#263)

Author: ValerianRey

src/torchjd/aggregation/graddrop.py

@@ -72,8 +72,8 @@ def _check_matrix_has_enough_rows(self, matrix: Tensor) -> None:
         n_rows = matrix.shape[0]
         if self.leak is not None and n_rows != len(self.leak):
             raise ValueError(
-                f"Parameter `matrix` should be a matrix of at least {len(self.leak)} rows "
-                f"(i.e. the number of leak scalars). Found `matrix` of shape `{matrix.shape}`."
+                f"Parameter `matrix` should be a matrix of exactly {len(self.leak)} rows (i.e. the "
+                f"number of leak scalars). Found `matrix` of shape `{matrix.shape}`."
             )
 
     def __repr__(self) -> str: