Use correct operator for testing intersection.

PotgresSQL supports array columns. The binary operator
`&&` checks if the operands have items in common.

I skipped writting a test that covers this behavior just because I don't think it's worth it. The whole gem is tested against a SqlLITE implementation and it would be cumbersome to bootstrap a PostgresSQL env just for this edge case. Mocking out the is also not really feasible.