Make the documentation consistent with the default limit

Author: DemiMarie

html5ever/src/tree_builder/mod.rs

@@ -134,7 +134,7 @@ pub struct TreeBuilderOpts {
     /// The maximum amount that the parser will process through the list
     /// of active formatting elements and the the stack of open elements.
     /// This is set to a finite number to prevent denial-of-service security
-    /// vulnerabilities.  0 is treated as the default (currently 10); any other
+    /// vulnerabilities.  0 is treated as the default (currently 20); any other
     /// value is used as-is.
     pub max_stack_depth: u8,