Add missing BUFFERS OFF in select_into regression tests

c2a4078 adjusted EXPLAIN ANALYZE to include BUFFERS by default, but
a few tests in select_into.sql neglected to add BUFFERS OFF.  The
failing tests seem unlikely to ever access buffers during execution, but
they certainly could during planning.

Per buildfarm member kestrel, tayra and calliphoridae.

Discussion: https://postgr.es/m/CANNMO++W7MM8T0KyXN3ZheXXt-uLVM3aEtZd+WNfZ=obxffUiA@mail.gmail.com

Author: david-rowley

src/test/regress/expected/select_into.out

@@ -37,7 +37,7 @@ EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF, BUFFERS OFF)
 -- WITH NO DATA, passes.
 CREATE TABLE selinto_schema.tbl_nodata1 (a) AS
   SELECT generate_series(1,3) WITH NO DATA;
-EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF, BUFFERS OFF)
   CREATE TABLE selinto_schema.tbl_nodata2 (a) AS
   SELECT generate_series(1,3) WITH NO DATA;
           QUERY PLAN           
@@ -50,7 +50,7 @@ EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
 PREPARE data_sel AS SELECT generate_series(1,3);
 CREATE TABLE selinto_schema.tbl_withdata3 (a) AS
   EXECUTE data_sel WITH DATA;
-EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF, BUFFERS OFF)
   CREATE TABLE selinto_schema.tbl_withdata4 (a) AS
   EXECUTE data_sel WITH DATA;
               QUERY PLAN              

src/test/regress/sql/select_into.sql

@@ -36,14 +36,14 @@ EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF, BUFFERS OFF)
 -- WITH NO DATA, passes.
 CREATE TABLE selinto_schema.tbl_nodata1 (a) AS
   SELECT generate_series(1,3) WITH NO DATA;
-EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF, BUFFERS OFF)
   CREATE TABLE selinto_schema.tbl_nodata2 (a) AS
   SELECT generate_series(1,3) WITH NO DATA;
 -- EXECUTE and WITH DATA, passes.
 PREPARE data_sel AS SELECT generate_series(1,3);
 CREATE TABLE selinto_schema.tbl_withdata3 (a) AS
   EXECUTE data_sel WITH DATA;
-EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF)
+EXPLAIN (ANALYZE, COSTS OFF, SUMMARY OFF, TIMING OFF, BUFFERS OFF)
   CREATE TABLE selinto_schema.tbl_withdata4 (a) AS
   EXECUTE data_sel WITH DATA;
 -- EXECUTE and WITH NO DATA, passes.