Remove duplicative polygon SP-GiST sequencing test.

Remove duplicative polygon SP-GiST sequencing test.

Code coverage comparisons confirm that the tests using
quad_poly_tbl_ord_seq1/quad_poly_tbl_ord_idx1 hit no code
paths not also covered by the similar tests using
quad_poly_tbl_ord_seq2/quad_poly_tbl_ord_idx2.  Since these
test cases are pretty expensive, they need to contribute more
than zero benefit.

In passing, make quad_poly_tbl_ord_seq2 a temp table, since
there seems little reason to keep it around after the test.

Discussion: https://postgr.es/m/735.1554935715@sss.pgh.pa.us