Docs: Synchronize documentation for `wp_get_attachment_image_attributes` filter callbacks in bundled themes:
* Twenty Sixteen: Correct the `$attachment` parameter type, use typed array notation.
* Twenty Seventeen: Correct the `$attachment` parameter type, use typed array notation.
* Twenty Nineteen: Correct the `@return` value type, use typed array notation.
* Twenty Twenty-One: Add missing `@return` value description, use typed array notation.
Follow-up to [29836], [47249], [49021], [49597].
Props ankitmaru, mukesh27, SergeyBiryukov.
Fixes #53878.
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