Add wait for new dataset to be created in test

`test_index_using_keys` doesn't seem to fail on local but fails on CI because it returns an empty object instead of the object with the size.
I wonder if this is because the dataset is not fully populated when checking and hopefully this will fix it.

lib/galaxy_test/api/test_datasets.py

@@ -24,7 +24,7 @@ def test_index(self):
 
     def test_index_using_keys(self):
         expected_keys = "size"
-        self.dataset_populator.new_dataset(self.history_id)
+        self.dataset_populator.new_dataset(self.history_id, wait=True)
         index_response = self._get(f"datasets?keys={expected_keys}")
         self._assert_status_code_is(index_response, 200)
         datasets = index_response.json()