Add API Gateway account ids

[rnhurt]

I've had problems in the past with "unknown" and "unremovable" ACM certificates living in my account. It turns out that creating an API Gateway automatically creates a cert using one of these accounts. It took me several days to figure this out, but now it appears as if there is an official AWS document showing this information. :+1:

Additional info: https://forums.aws.amazon.com/thread.jspa?threadID=315031&tstart=0

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[0xdabbad00]

Thank you @rnhurt !