Remove Backdrop raw queries test

Given that Smokey times out when running this test
And I need to make sure Smokey tests run successfully
And there is no need to run this test because @robyoung says there are
plenty of functional tests for this feature
Then we should remove this test as it is only intermittently successful
Merge pull request #111 from alphagov/remove-straight-pp-api-test

Remove Backdrop raw queries test