Fix: Update export wp

[Debarghya-Banerjee]

Trac Ticket: Core-36339

Overview:

• This PR enhances the export_wp function by refining the documentation and improving error handling for custom post types. The changes ensure clearer guidance for developers regarding the behavior of the function when invalid or non-exportable post types are specified.

Changes:

• Updated the doc block for export_wp to clarify:

  • The behavior when an invalid custom post type is supplied.
  • The consequences of supplying a valid custom post type that is not exportable.
  • Return a WP_Error for invalid or non-exportable post types.

Documentation:

Documentation updates have been made to reflect the changes in functionality and provide clear guidance for users of the export_wp function.

[github-actions]

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Props debarghyabanerjee.

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[github-actions]

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