Google Maps API key without proper referer restrictions is found in your repo. It can be embeded to anyone's website and if the billing account is active, it will incur charges on your account.
Visit the following link to verify that you can use the service with the key as below:
However with the proper restrictions, it should return a Forbidden error.
Unrestricted Services :-
Attacker is able to consume your daily free quota , charge your account and then abuse your key for their usage.