Modify grain_method description

To match level of detail of other documentation and to break down long lines.

src/api_core/data_request.py

@@ -68,7 +68,8 @@ def __init__(
         months: Months to include in the request.
         days: Days to include in the request.
         hours: Hours to include in the request.
-        grain_method: Determines what temporal grains (ie annual, monthly, daily) the user will accept if the grain the user requests is not implemented for a requested dataset. Options include, "strict", "skip", "any", "coarser", and "finer".
+        grain_method: A string indicating which other temporal grains to use if
+            the requested grain is not implemented for a requested dataset.
         subset_geom: A SubsetGeom representing the clipping region or points to
             use or None.
         target_crs: A CRS instance.