revert useless change

Signed-off-by: xinyual <xinyual@amazon.com>

Author: xinyual

core/src/main/java/org/opensearch/sql/calcite/utils/PlanUtils.java

@@ -219,8 +219,6 @@ static RelBuilder.AggCall makeAggCall(
       case AVG:
         return context.relBuilder.avg(distinct, null, field);
       case COUNT:
-        // return context.relBuilder.aggregateCall(SqlStdOperatorTable.APPROX_COUNT_DISTINCT,
-        // field);
         return context.relBuilder.count(
             distinct, null, field == null ? ImmutableList.of() : ImmutableList.of(field));
       case SUM: