Remove unnecessary test dependency on the contents of pg_pltemplate.

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.