pgsql: Remove unnecessary test dependency on the contents of pg_pltempl

Remove unnecessary test dependency on the contents of pg_pltemplate.

Using pg_pltemplate as test data was probably not very forward-looking,
considering we've had many discussions around removing that catalog
altogether. Use a nearby temp table instead, to make these two test
scripts more self-contained. This is a better test case anyway, since
it exercises the scenario where the entries in the anyarray column
actually vary in type intra-query.

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/bbd93667bde56d3900add55479759f33d20ece1e

Modified Files
--------------
src/test/regress/expected/json.out | 16 ++++++++++------
src/test/regress/expected/jsonb.out | 22 +++++++++++++---------
src/test/regress/sql/json.sql | 8 ++++++--
src/test/regress/sql/jsonb.sql | 16 ++++++++++------
4 files changed, 39 insertions(+), 23 deletions(-)