Fix prophet test (#1173)

The new version of prophet (1.1) introduced breaking changes to the fit
arguments.

http://b/237327883

Author: rosbo

tests/test_prophet.py

@@ -8,9 +8,11 @@
 class TestProphet(unittest.TestCase):
     def test_fit(self):
         train = pd.DataFrame({
-            'ds': np.array(['2012-05-18', '2012-05-20']),
-            'y': np.array([38.23, 21.25])
+            'ds': np.array(['2012-05-18', '2012-05-19', '2012-05-20', '2012-05-21', '2012-05-22']),
+            'y': np.array([38.23, 21.25, 20.18, 20.01, 19.02])
         })
 
         forecaster = Prophet(mcmc_samples=1)
-        forecaster.fit(train, control={'adapt_engaged': False})
+        forecaster.fit(train, adapt_engaged=False)
+
+        self.assertEqual(len(train) + 1, len(forecaster.make_future_dataframe(periods=1)))