pgsql: Remove excess space from jsonpath .datetime() default format str

Remove excess space from jsonpath .datetime() default format string

bffe1bd684 has introduced jsonpath .datetime() method, but default formats
for time and timestamp contain excess space between time and timezone. This
commit removes this excess space making behavior of .datetime() method
standard-compliant.

Discussion: https://postgr.es/m/94321be0-cc96-1a81-b6df-796f437f7c66%40postgrespro.ru
Author: Nikita Glukhov
Backpatch-through: 13

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/abcc0ab163003d2ab7c82a1e810ba257ebbec15f

Modified Files
--------------
src/backend/utils/adt/jsonpath_exec.c | 8 +--
src/test/regress/expected/jsonb_jsonpath.out | 76 ++++++++++++++--------------
src/test/regress/sql/jsonb_jsonpath.sql | 76 ++++++++++++++--------------
3 files changed, 80 insertions(+), 80 deletions(-)