Fix PostgreSQL range tests

The changes in c4044b2 meant the tests would error on a fresh DB.
Merge pull request #13393 from matthewd/fix_pg_range_tests

Fix PostgreSQL range tests on fresh DB

Correcting the name of the table we're creating is self-explanatory.

But we must also move away from the low IDs, because we're not touching the freshly-created primary key sequence; when the time comes, @new_range will be assigned an ID of 1.