Minor fix

Signed-off-by: kay <kay.kim@10gen.com>

Author: devkev

source/core/multikey-index-bounds.txt

@@ -324,7 +324,7 @@ Create a :ref:`compound index <index-type-compound>` on the
 
    db.survey3.ensureIndex( { "ratings.score.q1": 1, "ratings.score.q2": 1 } )
 
-The fields ``"ratings.score.q1"`` and ``"ratings.by.q2"`` share the
+The fields ``"ratings.score.q1"`` and ``"ratings.score.q2"`` share the
 field path ``"ratings.score"`` and the :query:`$elemMatch` must be on
 that path.