Remove duplicate entry for #717 in CHANGELOG

Author: blueyed

CHANGELOG.rst

@@ -313,10 +313,6 @@ time or change existing behaviors in order to make them less surprising/more use
   identify bugs in ``conftest.py`` files (`#1516`_). Thanks `@txomon`_ for
   the PR.
 
-* Add an 'E' to the first line of error messages from FixtureLookupErrorRepr.
-  Fixes `#717`_. Thanks `@blueyed`_ for reporting, `@eolo999`_ for the PR
-  and `@tomviner`_ for his guidance during EuroPython2016 sprint.
-
 * Text documents without any doctests no longer appear as "skipped".
   Thanks `@graingert`_ for reporting and providing a full PR (`#1580`_).