Fix docstring

package/visualization/plot_pyribs/__init__.py

@@ -25,7 +25,8 @@ def plot_grid_archive_heatmap(  # type: ignore
     Args:
         study: Optuna study with a sampler that uses pyribs. This function will
             plot the result archive from the sampler's scheduler.
-        ax: Axes on which to plot the heatmap. If None, we create a new axes.
+        ax: Axes on which to plot the heatmap. If None, we retrieve the current
+            axes.
         kwargs: All remaining kwargs will be passed to `grid_archive_heatmap
             <https://docs.pyribs.org/en/stable/api/ribs.visualize.grid_archive_heatmap.html>`_.
     Returns: