Update core.rst

fix a typo

Author: zm711

doc/source/core.rst

@@ -191,7 +191,7 @@ Relationship:
 
 :download:`Click here for a better quality SVG diagram <./images/simple_generated_diagram.svg>`
 
-.. note:: This figure do not include :class:`ChannelView` and :class:`RegionOfInterest`.
+.. note:: This figure does not include :class:`ChannelView` and :class:`RegionOfInterest`.
 
 For more details, see the :doc:`api_reference`.