pgsql: Remove reindex_catalog test from test schedules.

Remove reindex_catalog test from test schedules.

As the test currently causes occasional deadlocks (due to the schema
cleanup from previous sessions potentially still running), and the
patch from f912d7dec2 has gotten a fair bit of buildfarm coverage,
remove the test from the test schedules. There's a set of minor
releases coming up.

Leave the tests in place, so it can manually be run using EXTRA_TESTS.

For now also leave it in master, as there's no imminent release, and
there's plenty (re-)index related work in 12. But we'll have to
disable it before long there too, unless somebody comes up with simple
enough fixes for the deadlock (I'm about to post a vague idea to the
list).

Discussion: https://postgr.es/m/4622.1556982247@sss.pgh.pa.us
Backpatch: 9.4-11 (no master!)

Branch
------
REL9_5_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/8439589bc7e74e4687797da8c0e88455decf5463

Modified Files
--------------
src/test/regress/expected/reindex_catalog.out | 9 +++++++--
src/test/regress/parallel_schedule | 5 -----
src/test/regress/serial_schedule | 1 -
src/test/regress/sql/reindex_catalog.sql | 9 +++++++--
4 files changed, 14 insertions(+), 10 deletions(-)