Remove redundant test.

There is already a similar test in the 'partition' test in the main test
suite. Search for "-- Sub-partition insertion" in partition.sql to find
it.

src/test/tinc/tincrepo/mpp/gpdb/tests/storage/basic/partition/expected/mpp11341.ans

-drop table if exists MPP_11341;
-DROP TABLE
-create table MPP_11341 (i int, j int) with (appendonly = true)
-partition by range (j)
-( partition aa start (0) end(1000) every(500) with(appendonly=true)
-);
-NOTICE:  Table doesn't have 'DISTRIBUTED BY' clause -- Using column named 'i' as the Greenplum Database data distribution key for this table.
-HINT:  The 'DISTRIBUTED BY' clause determines the distribution of data. Make sure column(s) chosen are the optimal data distribution key to minimize skew.
-NOTICE:  CREATE TABLE will create partition "mpp_11341_1_prt_aa_1" for table "mpp_11341"
-NOTICE:  CREATE TABLE will create partition "mpp_11341_1_prt_aa_2" for table "mpp_11341"
-CREATE TABLE
-insert into MPP_11341 values(1,1);
-INSERT 0 1
-select * from MPP_11341_1_prt_aa_1;
- i | j 
----+---
- 1 | 1
-(1 row)
-
-insert into MPP_11341_1_prt_aa_1 values(1,1);
-INSERT 0 1
-select * from MPP_11341_1_prt_aa_1;
- i | j
----+---
- 1 | 1
- 1 | 1
-(2 rows)

src/test/tinc/tincrepo/mpp/gpdb/tests/storage/basic/partition/sql/mpp11341.sql

-drop table if exists MPP_11341;
-create table MPP_11341 (i int, j int) with (appendonly = true)
-partition by range (j)
-( partition aa start (0) end(1000) every(500) with(appendonly=true)
-);
-
-insert into MPP_11341 values(1,1);
-select * from MPP_11341_1_prt_aa_1;
-insert into MPP_11341_1_prt_aa_1 values(1,1);
-select * from MPP_11341_1_prt_aa_1;