pgsql: Remove test for pg_stat_reset_shared() in stats.sql

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 23c8c0c8f472 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

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a9a8108411e49c81316a9aba848a7f9ad3d3e939

Modified Files
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src/test/regress/expected/stats.out | 44 -------------------------------------
src/test/regress/sql/stats.sql      | 10 ---------
2 files changed, 54 deletions(-)