Minor docstring fixes

Author: jacobbieker

nowcasting_dataset/data_sources/optical_flow/optical_flow_data_source.py

@@ -212,7 +212,7 @@ def _update_dataarray_with_predictions(
             predictions: Predictions from the optical flow
 
         Returns:
-            The Xarray dataArray with the optical flow predictions
+            The Xarray DataArray with the optical flow predictions
         """
 
         # Combine all channels for a single timestep
@@ -239,7 +239,7 @@ def _compute_optical_flow(self, t0_image: np.ndarray, previous_image: np.ndarray
             previous_image: previous image to compute optical flow with
 
         Returns:
-            optical flow field
+            Optical Flow field
         """
         return cv2.calcOpticalFlowFarneback(
             prev=previous_image,