Restore vacuum_cleanup_index_scale_factor coverage.

Revert two recent commits that had btree_index.sql drop regression test
indexes rather than leave them behind for pg_dump testing.

This is intended to restore pg_upgrade coverage of indexes with the
vacuum_cleanup_index_scale_factor storage parameter set on buildfarm
member crake.

Backpatch: 11-12 only

Author: petergeoghegan

src/test/regress/expected/btree_index.out

@@ -312,8 +312,6 @@ select reloptions from pg_class WHERE oid = 'btree_idx1'::regclass;
  {vacuum_cleanup_index_scale_factor=70.0}
 (1 row)
 
-drop index btree_idx1;
-drop index btree_idx_err;
 --
 -- Test for multilevel page deletion
 --

src/test/regress/sql/btree_index.sql

@@ -140,8 +140,6 @@ create index btree_idx_err on btree_test(a) with (vacuum_cleanup_index_scale_fac
 -- Simple ALTER INDEX
 alter index btree_idx1 set (vacuum_cleanup_index_scale_factor = 70.0);
 select reloptions from pg_class WHERE oid = 'btree_idx1'::regclass;
-drop index btree_idx1;
-drop index btree_idx_err;
 
 --
 -- Test for multilevel page deletion