docs: update return value for Axes.axhspan and Axes.axvspan

Author: chrille0313

lib/matplotlib/axes/_axes.py

@@ -1006,14 +1006,14 @@ def axhspan(self, ymin, ymax, xmin=0, xmax=1, **kwargs):
 
         Returns
         -------
-        `~matplotlib.patches.Polygon`
+        `~matplotlib.patches.Rectangle`
             Horizontal span (rectangle) from (xmin, ymin) to (xmax, ymax).
 
         Other Parameters
         ----------------
-        **kwargs : `~matplotlib.patches.Polygon` properties
+        **kwargs : `~matplotlib.patches.Rectangle` properties
 
-        %(Polygon:kwdoc)s
+        %(Rectangle:kwdoc)s
 
         See Also
         --------
@@ -1061,14 +1061,14 @@ def axvspan(self, xmin, xmax, ymin=0, ymax=1, **kwargs):
 
         Returns
         -------
-        `~matplotlib.patches.Polygon`
+        `~matplotlib.patches.Rectangle`
             Vertical span (rectangle) from (xmin, ymin) to (xmax, ymax).
 
         Other Parameters
         ----------------
-        **kwargs : `~matplotlib.patches.Polygon` properties
+        **kwargs : `~matplotlib.patches.Rectangle` properties
 
-        %(Polygon:kwdoc)s
+        %(Rectangle:kwdoc)s
 
         See Also
         --------