Merge pull request statsmodels#5991 from bashtage/follow-up

MAINT: Remove comment no longer relevant

Author: bashtage

statsmodels/tsa/arima_model.py

@@ -1528,8 +1528,6 @@ def forecast(self, steps=1, exog=None, alpha=.05):
             2d array of the confidence interval for the forecast
         """
         if exog is not None:
-            # TODO: make a convenience function for this. we're using the
-            # pattern elsewhere in the codebase
             exog = array_like(exog, 'exog', maxdim=2)
             if self.k_exog == 1 and exog.ndim == 1:
                 exog = exog[:, None]