Revert "Prevent instability in contrib/pageinspect's regression test."

This reverts commit 5cda142bb9
(in v14 only).

It turns out that that fails under force_parallel_mode = regress,
because pageinspect's disk-access functions are marked parallel
safe, which they are not if you try to use them on a temp table.
The cost of fixing that pre-v15 seems to exceed the value of
making this test case fully stable, so we will just leave things
as-is in v14.

contrib/pageinspect/expected/page.out

@@ -1,6 +1,5 @@
 CREATE EXTENSION pageinspect;
--- Use a temp table so that effects of VACUUM are predictable
-CREATE TEMP TABLE test1 (a int, b int);
+CREATE TABLE test1 (a int, b int);
 INSERT INTO test1 VALUES (16777217, 131584);
 VACUUM (DISABLE_PAGE_SKIPPING) test1;  -- set up FSM
 -- The page contents can vary, so just test that it can be read

contrib/pageinspect/sql/page.sql

@@ -1,7 +1,6 @@
 CREATE EXTENSION pageinspect;
 
--- Use a temp table so that effects of VACUUM are predictable
-CREATE TEMP TABLE test1 (a int, b int);
+CREATE TABLE test1 (a int, b int);
 INSERT INTO test1 VALUES (16777217, 131584);
 
 VACUUM (DISABLE_PAGE_SKIPPING) test1;  -- set up FSM