Try to stabilize the reloptions test.

Where we test vacuum_truncate's effects, sometimes this is failing to
truncate as expected on the build farm.  That could be explained by page
skipping, so disable it explicitly, with the theory that commit fe246d1c
didn't go far enough.

Back-patch to 12, where the vacuum_truncate tests were added.

Discussion: https://postgr.es/m/CA%2BhUKGLT2UL5_JhmBzUgkdyKfc%3D5J-gJSQJLysMs4rqLUKLAzw%40mail.gmail.com

src/test/regress/expected/reloptions.out

@@ -103,7 +103,7 @@ INSERT INTO reloptions_test VALUES (1, NULL), (NULL, NULL);
 ERROR:  null value in column "i" of relation "reloptions_test" violates not-null constraint
 DETAIL:  Failing row contains (null, null).
 -- Do an aggressive vacuum to prevent page-skipping.
-VACUUM FREEZE reloptions_test;
+VACUUM (FREEZE, DISABLE_PAGE_SKIPPING) reloptions_test;
 SELECT pg_relation_size('reloptions_test') > 0;
  ?column? 
 ----------
@@ -129,7 +129,7 @@ INSERT INTO reloptions_test VALUES (1, NULL), (NULL, NULL);
 ERROR:  null value in column "i" of relation "reloptions_test" violates not-null constraint
 DETAIL:  Failing row contains (null, null).
 -- Do an aggressive vacuum to prevent page-skipping.
-VACUUM FREEZE reloptions_test;
+VACUUM (FREEZE, DISABLE_PAGE_SKIPPING) reloptions_test;
 SELECT pg_relation_size('reloptions_test') = 0;
  ?column? 
 ----------

src/test/regress/sql/reloptions.sql

@@ -62,7 +62,7 @@ CREATE TABLE reloptions_test(i INT NOT NULL, j text)
 SELECT reloptions FROM pg_class WHERE oid = 'reloptions_test'::regclass;
 INSERT INTO reloptions_test VALUES (1, NULL), (NULL, NULL);
 -- Do an aggressive vacuum to prevent page-skipping.
-VACUUM FREEZE reloptions_test;
+VACUUM (FREEZE, DISABLE_PAGE_SKIPPING) reloptions_test;
 SELECT pg_relation_size('reloptions_test') > 0;
 
 SELECT reloptions FROM pg_class WHERE oid =
@@ -73,7 +73,7 @@ ALTER TABLE reloptions_test RESET (vacuum_truncate);
 SELECT reloptions FROM pg_class WHERE oid = 'reloptions_test'::regclass;
 INSERT INTO reloptions_test VALUES (1, NULL), (NULL, NULL);
 -- Do an aggressive vacuum to prevent page-skipping.
-VACUUM FREEZE reloptions_test;
+VACUUM (FREEZE, DISABLE_PAGE_SKIPPING) reloptions_test;
 SELECT pg_relation_size('reloptions_test') = 0;
 
 -- Test toast.* options