Update persistent TPM & UEFI page to clarify storageclass requirements

[ianb-mp]

What this PR does / why we need it:

Update Persistent TPM and UEFI state to reflect the changes made in kubevirt/kubevirt#11773

Also, small spelling fix: prerequesites -> prerequisites

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

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[kubevirt-bot]

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[kubevirt-bot]

Hi @ianb-mp. Thanks for your PR.

I'm waiting for a kubevirt member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ianb-mp]

I was unsure if the following statement is still true - can anyone confirm?

Backend storage is currently incompatible with VM snapshot. It is planned to add snapshot support in the future.

[akalenyu]

I was unsure if the following statement is still true - can anyone confirm?

Backend storage is currently incompatible with VM snapshot. It is planned to add snapshot support in the future.

I think so - https://github.com/kubevirt/kubevirt/blob/effcb5b8e6fc951ec5c85ba47ad1daedc0173d79/pkg/virt-api/webhooks/validating-webhook/admitters/vmsnapshot-admitter.go#L166-L174
/cc @jean-edouard