wp_title_rss( string $deprecated = '–' )

function wp_title_rss( $deprecated = '–' ) {
	if ( '–' !== $deprecated ) {
		/* translators: %s: 'document_title_separator' filter name */
		_deprecated_argument( __FUNCTION__, 'WP-4.4.0', sprintf( __( 'Use the %s filter instead.' ), '<code>document_title_separator</code>' ) );
	}

	/**
	 * Filters the blog title for display of the feed title.
	 *
	 * @since WP-2.2.0
	 * @since WP-4.4.0 The `$sep` parameter was deprecated and renamed to `$deprecated`.
	 *
	 * @see get_wp_title_rss()
	 *
	 * @param string $wp_title_rss The current blog title.
	 * @param string $deprecated   Unused.
	 */
	echo apply_filters( 'wp_title_rss', get_wp_title_rss(), $deprecated );
}