As of July 16, 2018, in order to continue using the Google Maps Platform APIs, you must enable billing on each of your projects. If you choose not to add a billing account, your maps will contain "For development purposes only" message.
Googlemaps API key is needed for built-in theme map element offering extended options for map style, zoom and marker.
However, you may use a standard Google Maps element of WPBakery page builder which does not require API key.
All you need is to find your location on Googlemaps website, open its burger menu in the top left corner and select " Share or embed map" in the list. Then copy the HTML code in "Embed a map" tab: