As you may be aware, Google starts to use Firebase as analytics so I want to use it in my current project. I succesfully finished the implementation and upload project to iT
If the library that you're using has any calls to the push notification API and you don't have a provisioning profile/certificate that enables your app to receive push notifications then you will receive this email from Apple. However if you do not need to use push notifications in your app then you can ignore this email.
This email doesn't mean that your app will be rejected. I used to get this email all of the time when submitting games made with Unity and using a certain Prime31 plugin for native functionality, it also made use of the push notification API which caused me to receive this email.
You can ignore it, it will be fine.