Drop default value from docstring of imshow.

tillahoffmann · timhoffm · web-flow · commit dff75624d584 · 2019-09-09T10:04:05.000+01:00
Co-Authored-By: Tim Hoffmann &lt;2836374+timhoffm@users.noreply.github.com&gt;
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -5504,7 +5504,7 @@ def imshow(self, X, cmap=None, norm=None, aspect=None,
             which can be set by *filterrad*. Additionally, the antigrain image
             resize filter is controlled by the parameter *filternorm*.
 
-        alpha : scalar or array_like, optional, default: None
+        alpha : scalar or array-like, optional
             The alpha blending value, between 0 (transparent) and 1 (opaque).
             If *alpha* is an array, the alpha blending values are applied pixel
             by pixel, and *alpha* must have the same shape as *X*.
