Include Customer Success as CC of API Limit Notification Emails

[asaphko]

Following https://github.com/Flagsmith/infrastructure/issues/334 - we want to add our CS team as a CC to the emails that are sent regarding API limits usage.

[matthewelwell]

I've added a PR for this here, but I actually wonder if we should bcc rather than cc? It might be weird for customers to see the emails going to them with cs@flagsmith.com cc'd?