Use $this instead of $block

Co-authored-by: Niels de Blaauw <niels.de.blaauw@gmail.com>

Author: jmslbam

src/Gutenberg/Block_Type.php

@@ -118,7 +118,7 @@ public function clarkson_render_callback( $attributes, $content ) {
 			);
 		}
 		if ( is_callable( $this->original_render_callback ) ) {
-			return (string) call_user_func( $this->original_render_callback, $attributes, $content, $block );
+			return (string) call_user_func( $this->original_render_callback, $attributes, $content, $this );
 		}
 		return $content;
 	}