Update Device.model_name doc (#637)

Author: rly

core/nwb.device.yaml

@@ -25,8 +25,8 @@ groups:
   - name: model_name
     dtype: text
     doc: DEPRECATED. The model name of the device, e.g., Neuropixels 1.0, V-Probe, Bergamo III.
-      Instead of using this field, storing the value in DeviceModel.name and link to that 
-      DeviceModel from this Device. 
+      Instead of using this field, create and add a new DeviceModel named the model name and 
+      link to that DeviceModel from this Device.
     required: false
   - name: serial_number
     dtype: text