DOCSP-13270 SQL Syntax correction on agg group page (#2400)

Author: ianf-mongodb

source/reference/operator/aggregation/group.txt

@@ -319,7 +319,8 @@ This aggregation operation is equivalent to the following SQL statement:
           Avg(quantity)             AS averageQuantity,
           Count(*)                  AS Count
    FROM   sales
-   GROUP  BY Date(date)
+   WHERE date >= '01/01/2014' AND date < '01/01/2015'
+   GROUP  BY date
    ORDER  BY totalSaleAmount DESC
 
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