Removed old docs

docs/building_your_site/frontenddevelopers.rst

@@ -181,17 +181,6 @@ The available resizing methods are:
 
         Leaves the image at its original size - no resizing is performed.
 
-    ``smart`` 
-        (takes two dimensions)
-
-        .. code-block:: django
-
-            {% image self.photo smart-200x200 %}
-
-        Similar to ``fill`` but resizes and crops based on the contents of the image.
-
-        This will perform face and feature detection using OpenCV which must be installed in order for the smart filter to work.
-
 
 .. Note::
     Wagtail does not allow deforming or stretching images. Image dimension ratios will always be kept. Wagtail also *does not support upscaling*. Small images forced to appear at larger sizes will "max out" at their their native dimensions.