Finish reverting "Insert temporary debugging output in regression tests."

This removes the last of the temporary debugging queries added to the
regression tests by commit f03a9ca43.  We've pretty much convinced
ourselves that the plan instability we were seeing is due to VACUUM
sometimes failing to update relpages/reltuples for a single-page table,
due to bgwriter or checkpointer holding a pin on that page at just the
wrong time.  I'll push a workaround for that separately.

Discussion: https://postgr.es/m/CA+hUKG+0CxrKRWRMf5ymN3gm+BECHna2B-q1w8onKBep4HasUw@mail.gmail.com

src/test/regress/expected/select_parallel.out

@@ -89,20 +89,6 @@ select round(avg(aa)), sum(aa) from a_star a3;
     14 | 355
 (1 row)
 
--- Temporary hack to investigate whether extra vacuum/analyze is happening
-select relname, relpages, reltuples
-from pg_class
-where relname like '__star' order by relname;
- relname | relpages | reltuples 
----------+----------+-----------
- a_star  |        1 |         3
- b_star  |        1 |         4
- c_star  |        1 |         4
- d_star  |        1 |        16
- e_star  |        1 |         7
- f_star  |        1 |        16
-(6 rows)
-
 -- Disable Parallel Append
 alter table a_star reset (parallel_workers);
 alter table b_star reset (parallel_workers);

src/test/regress/sql/select_parallel.sql

@@ -36,11 +36,6 @@ explain (costs off)
   select round(avg(aa)), sum(aa) from a_star;
 select round(avg(aa)), sum(aa) from a_star a3;
 
--- Temporary hack to investigate whether extra vacuum/analyze is happening
-select relname, relpages, reltuples
-from pg_class
-where relname like '__star' order by relname;
-
 -- Disable Parallel Append
 alter table a_star reset (parallel_workers);
 alter table b_star reset (parallel_workers);