Rotate credentials for 'io-datastores' Kubernetes cluster

As per following notice from GCP sent to some owners of the apache-beam-testing project, credentials if the Kubernetes cluster used for testing will expire on 03/02/2022 if no action is taken and some test suites might start failing.

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Our records show that the CA for the following cluster(s) in your project(s) will expire soon:

Apache Beam Testing (apache-beam-testing)
Cluster: io-datastores CA will expire on Wed Mar 2 11:48:44 AM PST 2022.
To prevent normal cluster operations from being interrupted, please take these steps before the CA’s expiration:

Perform a credential rotation on the above clusters.
Update all API clients outside of the clusters (such as kubectl on developer machines) to use the new credentials once credential rotation has been initiated.
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