axes: correct return value in scatter docstring

Author: akhmerov

lib/matplotlib/axes.py

@@ -6044,7 +6044,7 @@ def scatter(self, x, y, s=20, c='b', marker='o', cmap=None, norm=None,
 
         %(Collection)s
 
-        A :class:`~matplotlib.collections.Collection` instance is
+        A :class:`~matplotlib.collections.PathCollection` instance is
         returned.
         """