Remove reference to now-deleted class method.

Author: Viper007Bond

syntaxhighlighter.php

@@ -55,7 +55,6 @@ function __construct() {
 		add_filter( 'bp_get_the_topic_post_edit_text', array( $this, 'decode_shortcode_contents' ), 1 ); // BuddyPress
 
 		// Outputting SyntaxHighlighter's JS and CSS
-		add_action( 'admin_head', array( $this, 'output_header_placeholder' ), 15 ); // For comments
 		add_action( 'wp_footer', array( $this, 'maybe_output_scripts' ), 15 );
 		add_action( 'admin_footer', array( $this, 'maybe_output_scripts' ), 15 ); // For comments