Document/Backport support SHA-256 thumbprints when connecting to the vSphere API

[lubronzhan]

What would you like to be added?

Document the support of SHA-256 on 1.30+, also backport to previous branch if needed

Why is this needed?

golang 1.24 is deprecating sha1 signiture kubernetes/kubernetes#125689
govmomi also starts to support sha256 thumbprint in 0.36.1. https://github.com/vmware/govmomi/releases/tag/v0.36.1

CPI used to support sha1 vsphere cert thumbprint to validate certificate. only 1.30 and main branch use govmomi 0.37.3, need to backport/document to other previous version if needed

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