Remove test for pg_stat_reset_shared() in stats.sql

Some buildfarm members have been failing a test related to pg_stat_io,
as an effect of 23c8c0c that has switched pg_stat_reset_shared()
from being a no-op to reset all shared stats types.

This extra reset has the effect to make pg_stat_io's counters low enough
that little concurrent activity is enough to cause a failure.  Another
thing I have considered is to move this sequence at the end of
stats.sql, but there are other instabilities, one being pg_stat_wal.

Knowing that there are already tests for the reset of each individual
shared stats target, this test has limited value, so let's remove it to
minimize the number of resets done for each shared stats type.  This
should hopefully improve the stability of the whole.

Discussion: https://postgr.es/m/3500949.1700935734@sss.pgh.pa.us

Author: michaelpq

src/test/regress/expected/stats.out

@@ -990,50 +990,6 @@ SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 (1 row)
 
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
--- Test that reset_shared with no argument resets all the stats types
--- supported (providing NULL as argument has the same effect).
-SELECT pg_stat_reset_shared();
- pg_stat_reset_shared 
-----------------------
- 
-(1 row)
-
-SELECT stats_reset > :'archiver_reset_ts'::timestamptz FROM pg_stat_archiver;
- ?column? 
-----------
- t
-(1 row)
-
-SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
- ?column? 
-----------
- t
-(1 row)
-
-SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
- ?column? 
-----------
- t
-(1 row)
-
-SELECT stats_reset > :'recovery_prefetch_reset_ts'::timestamptz FROM pg_stat_recovery_prefetch;
- ?column? 
-----------
- t
-(1 row)
-
-SELECT max(stats_reset) > :'slru_reset_ts'::timestamptz FROM pg_stat_slru;
- ?column? 
-----------
- t
-(1 row)
-
-SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
- ?column? 
-----------
- t
-(1 row)
-
 -- Test error case for reset_shared with unknown stats type
 SELECT pg_stat_reset_shared('unknown');
 ERROR:  unrecognized reset target: "unknown"

src/test/regress/sql/stats.sql

@@ -494,16 +494,6 @@ SELECT pg_stat_reset_shared('wal');
 SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
 SELECT stats_reset AS wal_reset_ts FROM pg_stat_wal \gset
 
--- Test that reset_shared with no argument resets all the stats types
--- supported (providing NULL as argument has the same effect).
-SELECT pg_stat_reset_shared();
-SELECT stats_reset > :'archiver_reset_ts'::timestamptz FROM pg_stat_archiver;
-SELECT stats_reset > :'bgwriter_reset_ts'::timestamptz FROM pg_stat_bgwriter;
-SELECT stats_reset > :'checkpointer_reset_ts'::timestamptz FROM pg_stat_checkpointer;
-SELECT stats_reset > :'recovery_prefetch_reset_ts'::timestamptz FROM pg_stat_recovery_prefetch;
-SELECT max(stats_reset) > :'slru_reset_ts'::timestamptz FROM pg_stat_slru;
-SELECT stats_reset > :'wal_reset_ts'::timestamptz FROM pg_stat_wal;
-
 -- Test error case for reset_shared with unknown stats type
 SELECT pg_stat_reset_shared('unknown');