[EKS] [BUG]: CSR is not returning the certificate after approval in 1.21

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### Description

This is a potential bug, as a) it doesn't match the service expectations; b) it doesn't happen with any previous EKS version; c) it works as expected on other, non-EKS 1.21s.

Essentially, upon submitting a Certificate Signing Request, EKS 1.21 is returning success but not including the certificate in the CSR's `.status.certificate` field. To reproduce please try to run:

```sh
cd /tmp
cat <

No repository file or test is named. Start by running the supplied cfssl and kubectl reproduction against EKS 1.21, then read the linked StackGres issue for context; done means establishing whether the CSR's status.certificate is returned or documenting the upstream resolution.

Written by the indexing model from the issue text.