Supply callback to Google Maps API to avoid console error

[derat]

The Maps API logs an error on page load now:

Loading the Google Maps JavaScript API without a callback is not supported: https://developers.google.com/maps/documentation/javascript/url-params#required_parameters

From the linked docs:

The following parameters are required when loading the Maps JavaScript API.

• key: Your API key. The Maps JavaScript API will not load unless a valid API key is specified.
• callback: The name of a global function to be called once the Maps JavaScript API loads completely.

No clue why they just changed this, but it sounds like it's easy to fix: https://stackoverflow.com/questions/75179573/