Fix test failing with Dakota 6.9

[mdpiper]

I recently built conda binaries for Dakota 6.9. However, using this version of Dakota (where previously v6.4 was used) causes a test, test_dakota.test_running_in_different_directory, to fail. The only difference between passing and failing is the Dakota version. This isn't quite a dakotathon issue, since I list support for Dakota 6.4, but the test should be updated to work for v6.9, as well.