Fix UT

Author: Subham Singhal

datafusion/sqllogictest/test_files/subquery.slt

@@ -689,10 +689,8 @@ query TT
 explain SELECT t1_id, (SELECT t2_id FROM t2 limit 0) FROM t1
 ----
 logical_plan
-01)Projection: t1.t1_id, __scalar_sq_1.t2_id AS t2_id
-02)--Left Join: 
-03)----TableScan: t1 projection=[t1_id]
-04)----EmptyRelation: rows=0
+01)Projection: t1.t1_id, Int32(NULL) AS t2_id
+02)--TableScan: t1 projection=[t1_id]
 
 query II rowsort
 SELECT t1_id, (SELECT t2_id FROM t2 limit 0) FROM t1