Add a set of credentials without `dataset.create` permissions

[j-bennet]

We need a new set of credentials for dask-bigquery CI to test a use case when user can create tables in an existing dataset, but not create a new dataset.

Can you help with this one @ntabris?

cc @ncclementi

Related to #75

[ntabris]

Can you help with this one @ntabris?

You have full permissions in the relevant GCP project, feel free to put something on my calendar if you'd like me to help w/ this though.