Fix memory leak in fmpz_poly/test/t-discriminant.
Fix memory leak in fmpz_poly/test/t-discriminant.

fredrik-johansson/flint2,fredrik-johansson/flint2,jpflori/flint2,dsroche/flint2,wbhart/flint2,dsroche/flint2,jpflori/flint2,jpflori/flint2,wbhart/flint2,dsroche/flint2,fredrik-johansson/flint2,wbhart/flint2,dsroche/flint2,jpflori/flint2