Add note about setting correct kubelet work dir for k0s to documentation & fix name of helm parameter in docs

[soenkeliebau]

Description

K0s has a non default kubelet work dir which needs to be configured when deploying secret operator.

The name of the helm chart parameter was refactored to be csiNodeDriver.kubeletDir instead of kubeletDir, but the docs not updated, this PR fixes that.

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Reviewer

• Documentation added or updated. Follows the style guide.

Acceptance

• Feature Tracker has been updated
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[sbernauer]

Thanks!
It would be great if we backport this to the 25.11 release branch to fix the docs

[soenkeliebau]

When released we can add anchor links to stackabletech/documentation#819