fix no pushdown rex explain IT

Signed-off-by: Jialiang Liang <[email protected]>

Author: RyanL1997

integ-test/src/test/resources/expectedOutput/calcite_no_pushdown/explain_rex.yaml

@@ -3,10 +3,10 @@ calcite:
     LogicalSystemLimit(fetch=[10000], type=[QUERY_SIZE_LIMIT])
       LogicalProject(account_number=[$0], firstname=[$1], address=[$2], balance=[$3], gender=[$4], city=[$5], employer=[$6], state=[$7], age=[$8], email=[$9], lastname=[$10], initial=[$17])
         LogicalSort(fetch=[5])
-          LogicalProject(account_number=[$0], firstname=[$1], address=[$2], balance=[$3], gender=[$4], city=[$5], employer=[$6], state=[$7], age=[$8], email=[$9], lastname=[$10], _id=[$11], _index=[$12], _score=[$13], _maxscore=[$14], _sort=[$15], _routing=[$16], initial=[REX_EXTRACT($10, '(?<initial>^[A-Z])', 1)])
+          LogicalProject(account_number=[$0], firstname=[$1], address=[$2], balance=[$3], gender=[$4], city=[$5], employer=[$6], state=[$7], age=[$8], email=[$9], lastname=[$10], _id=[$11], _index=[$12], _score=[$13], _maxscore=[$14], _sort=[$15], _routing=[$16], initial=[REX_EXTRACT($10, '(?<initial>^[A-Z])', 'initial')])
             CalciteLogicalIndexScan(table=[[OpenSearch, opensearch-sql_test_index_account]])
   physical: |
     EnumerableLimit(fetch=[10000])
-      EnumerableCalc(expr#0..16=[{inputs}], expr#17=['(?<initial>^[A-Z])'], expr#18=[1], expr#19=[REX_EXTRACT($t10, $t17, $t18)], proj#0..10=[{exprs}], initial=[$t19])
+      EnumerableCalc(expr#0..16=[{inputs}], expr#17=['(?<initial>^[A-Z])'], expr#18=['initial'], expr#19=[REX_EXTRACT($t10, $t17, $t18)], proj#0..10=[{exprs}], initial=[$t19])
         EnumerableLimit(fetch=[5])
           CalciteEnumerableIndexScan(table=[[OpenSearch, opensearch-sql_test_index_account]])