remove "is the result" typo

Remove duplicate "is the result" in _Evaluating a grouped field set_ > _Field entries_.

Author: benbjohnson

spec/Section 6 -- Execution.md

@@ -118,7 +118,7 @@ will be an entry in this map for every item in the grouped field set.
 ### Field entries
 
 Each item in the grouped field set can potentially create an entry in the
-result map. That entry in the result map is the result is the result of calling
+result map. That entry in the result map is the result of calling
 `GetFieldEntry` on the corresponding item in the grouped field set.
 `GetFieldEntry` can return `null`, which indicates that there should be no
 entry in the result map for this item. Note that this is distinct from