BUG #19338: [PG15] Unstable SQL result in test regress/tablespace

The following bug has been logged on the website:

Bug reference:      19338
Logged by:          Dmitry Kovalenko
Email address:      d.kovalenko@postgrespro.ru
PostgreSQL version: 15.15
Operating system:   AltLinux-10 ARM64
Description:        

Hello!

PG15 has an unstable SQL in test regress/tablespace:

^^^^^^^^^^^^^^^^^^^^/home/test/.../src/test/regress/regression.diffs
diff -U3 /home/test/.../src/test/regress/expected/tablespace.out
/home/test/.../src/test/regress/results/tablespace.out
--- /home/test/.../src/test/regress/expected/tablespace.out     2025-11-30
21:11:56.000000000 +0300
+++ /home/test/.../src/test/regress/results/tablespace.out      2025-11-30
23:17:49.378004420 +0300
@@ -334,9 +334,9 @@
     where c.reltablespace = t.oid AND c.relname LIKE 'part%_idx';
    relname   |     spcname
 -------------+------------------
+ part_a_idx  | regress_tblspace
  part1_a_idx | regress_tblspace
  part2_a_idx | regress_tblspace
- part_a_idx  | regress_tblspace
 (3 rows)
 
 \d testschema.part
^^^^^^^^^^^^^^^^^^^^

https://github.com/postgres/postgres/blob/134a8ee2240557e8165cffe70d19e48937cece03/src/test/regress/sql/tablespace.sql#L228

---
PG16 has the correct SQL:
     ...
     where c.reltablespace = t.oid AND c.relname LIKE 'part%_idx' ORDER BY
relname;

https://github.com/postgres/postgres/blob/4d288e33b957ce5023dd1ec24b53f02c8a9e8ba0/src/test/regress/sql/tablespace.sql#L226

Could you backport this fix from PG16 to PG15, please?

Thanks&Regards,
Dmitry Kovalenko