LibHTML: Hide debugging output unless HTML_DEBUG is defined

Author: https://github.com/bugaevc
Commit: 6491493e26
Pull-request: https://github.com/SerenityOS/serenity/pull/609
Reviewed-by: https://github.com/awesomekling ✅

Libraries/LibHTML/Dump.h

@@ -9,3 +9,5 @@ void dump_tree(const Node&);
 void dump_tree(const LayoutNode&);
 void dump_sheet(const StyleSheet&);
 void dump_rule(const StyleRule&);
+
+#undef HTML_DEBUG