API EDR Radius query needs to extra text

[chris-little]

Please change the text The radius query resource returns data for a defined radius. The resource offers a convenience mechanism for querying the API by radius. to The radius query resource returns all data within a defined radius of a position. The resource offers a convenience mechanism for querying the API by a specialised form of the Area query. Like the Position and Area queries, it can have a vertical or temporal extent.