Docs: Restore the @return tag for WP_Duotone::is_preset()

[jigneshbhavani]

WP_Duotone::is_preset() carries two @param tags for the same variable, giving contradictory types, and documents no return value at all:

 * @param string $duotone_attr The duotone attribute from a block.
 * @param string|string[] $duotone_attr The duotone attribute from a block.
 */
private static function is_preset( $duotone_attr ) {

In [61603] the type was widened from string to string|string[], but the new tag replaced the @return line rather than the old @param:

-	 * @return bool True if the duotone preset present and valid.
+	 * @param string|string[] $duotone_attr The duotone attribute from a block.

So the method lost its return documentation and kept a stale parameter type in the same edit.

Fix

Drop the stale @param and restore the @return. The wording is the one [61603] removed, so nothing here is invented. Two independent references confirm it:

• WP_Duotone::get_slug_from_attribute(), immediately above, was updated by that same changeset and got it right: @param string|string[] and a @return.
• The Gutenberg counterpart, lib/class-wp-duotone-gutenberg.php, still reads @param string|string[] $duotone_attr and @return bool True if the duotone preset present and valid.

string|string[] is the correct type. The method guards with ! is_string( $duotone_attr ) and returns false, which is exactly the array case [61603] was written to handle.

No functional change. phpcs passes on the file.

Trac ticket: https://core.trac.wordpress.org/ticket/64896

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5
Used for: Scanning src/ for docblock and signature disagreements, which is how this was found, and drafting this description. I confirmed the cause in the changeset history, checked the wording against the sibling method and the Gutenberg copy, ran phpcs, and I take responsibility for the change.

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