Fix syntax error in ImageRenditionField example

CONTRIBUTORS.rst

@@ -261,6 +261,7 @@ Contributors
 * Ross Crawford-d'Heureuse
 * rifuso
 * Jon Carmack
+* Martin Sandström
 
 Translators
 ===========

docs/advanced_topics/api/v2/configuration.rst

@@ -204,7 +204,7 @@ For example:
 
 .. code-block:: python
 
-    from wagtail.wagtailimages.api.fields.ImageRenditionField
+    from wagtail.wagtailimages.api.fields import ImageRenditionField
 
     class BlogPage(Page):
         ...