pgsql: Stabilize just-added regression test cases.

Stabilize just-added regression test cases.

The tests added by commits 029dea882 et al turn out to produce
different output under -DRANDOMIZE_ALLOCATED_MEMORY. This is
not a bug exactly: that flag causes coerce_type() to invoke
the input function twice when coercing an unknown-type literal
to a specific type. So you get tsqueryin's bleat about an empty
tsquery twice. Revise the test query to avoid that.

Discussion: /messages/by-id/20230406213813.uep7plg6lvcywujo@awork3.anarazel.de

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/83965ef0bd2345f83d728f0ca80779b8fd1c264c

Modified Files
--------------
src/test/regress/expected/tsearch.out | 8 ++------
src/test/regress/sql/tsearch.sql | 4 ++--
2 files changed, 4 insertions(+), 8 deletions(-)