Docs: Warn that switching storage strategies is not supported

[AObuchow]

Is your task related to a problem? Please describe

Switching between persistent storage strategies (per-user -> per-workspace, or vice versa) is not supported by Che and can lead to orphaned data. The only storage strategy switching that's supported is ephemeral (non-persistent) -> per-user OR per-workspace.

Describe the solution you'd like

We should mention this limitation in the configuring storage strategy page so that users don't accidentally orphan their data.

Describe alternatives you've considered

No response

Additional context

This is related to #23002, as users might encounter a pvc multi-attach error when using the per-user storage strategy and then decide to switch to the per-user storage strategy, resulting in data loss.

[AObuchow]

@deerskindoll I'll gladly help you make this docs update :)