Docs: Fix inline documentation standards in wp-admin

[huzaifaalmesbah]

Ticket: https://core.trac.wordpress.org/ticket/64224

Changes

• class-wp-importer.php: Added missing file header.
• media.php: Fixed missing @param/@global descriptions and @return format.
• class-wp-list-table.php: Added missing summaries and fixed formatting.
• user.php: Added missing @param/@global descriptions.

[github-actions]

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[github-actions]

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