Revert "Stabilize test of BRIN parallel create"

This reverts commit 4d916dd876. The goal of that commit was to
stabilize a test of parallel BRIN build, but using a TEMPORARY table
disables parallel index builds on that table, making the test useless.

Discussion: https://postgr.es/m/95d9cd43-5a92-407c-b7e4-54cd303630fe%40enterprisedb.com

contrib/pageinspect/expected/brin.out

@@ -109,7 +109,7 @@ SELECT (COUNT(*) = (SELECT relpages FROM pg_class WHERE relname = 'test2')) AS r
 DROP TABLE test1;
 DROP TABLE test2;
 -- Test that parallel index build produces the same BRIN index as serial build.
-CREATE TEMPORARY TABLE brin_parallel_test (a int, b text, c bigint) WITH (fillfactor=40);
+CREATE TABLE brin_parallel_test (a int, b text, c bigint) WITH (fillfactor=40);
 -- Generate a table with a mix of NULLs and non-NULL values (and data suitable
 -- for the different opclasses we build later).
 INSERT INTO brin_parallel_test

contrib/pageinspect/sql/brin.sql

@@ -56,7 +56,7 @@ DROP TABLE test1;
 DROP TABLE test2;
 
 -- Test that parallel index build produces the same BRIN index as serial build.
-CREATE TEMPORARY TABLE brin_parallel_test (a int, b text, c bigint) WITH (fillfactor=40);
+CREATE TABLE brin_parallel_test (a int, b text, c bigint) WITH (fillfactor=40);
 
 -- Generate a table with a mix of NULLs and non-NULL values (and data suitable
 -- for the different opclasses we build later).