Update registration description

[YuliyaPoznyak]

No description provided.

[georged]

@YuliyaPoznyak we're not migrating data or solution. It's about moving the website between deployments. That key is important because we encrypt sensitive information using it. If it's not present it will be generated for every new installation and we won't be able to retrieve app secret. The text should read:

Important Information for site migration

If you are planning to migrate your website between deployments, make sure to set ICDS_AUTH_KEY in Advanced Settings before connecting the plugin to Dataverse. This key is used to encrypt sensitive information stored in the plugin configuration. If it is not present, the plugin will not be able to automatically reconnect to Dataverse after the migration.

After the site migration, ensure you re-register the site in Dataverse. Multiple site registrations are supported, allowing connections from both the original site and the copy at the same time.

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Also, can we use https://docusaurus.io/docs/2.x/markdown-features/admonitions to highlight this block? Like:

:::note Important Information for site migration

Content 

:::