Update documentation as default is RSA for cluster.serviceaccount in Talos >=1.7

[eriklundai]

Bug Report

Not really a bug, just incorrect documentation.

Description

The documentation for Google Workload Identity is wrongly specifying that Talos by default uses “ ECDSA keys for Kubernetes service account verification”.
This is wrong as Talos version >=1.7 defaults to RSA.

See also change of default algorithm in PR-8223
Link tó documentation: Kubernetes Guide, GCP Workload identity

• Talos version: >=1.7