Update pipeline default value (#111)

Author: jordan-smith721

source/source-connector/configuration-properties/change-stream.txt

@@ -56,7 +56,7 @@ Settings
           - :ref:`<source-usage-example-custom-pipeline>`
           - :ref:`<source-usage-example-multiple-sources>`
 
-       | **Default**: ``[]``
+       | **Default**: ``"[]"``
        | **Accepted Values**: Valid aggregation pipeline stage
 
    * - | **change.stream.full.document**