[css-cascade-6][editorial] Fix heading levels

Author: mirisuzanne

css-cascade-6/Overview.bs

@@ -231,7 +231,7 @@ Layer Ordering</h4>
 -->
 
 <h3 id='scoped-styles'>
-Scoped Styles</h2>
+Scoped Styles</h3>
 
 	A <dfn>scope</dfn> is a subtree or fragment of a document,
 	which can be used by selectors for more targeted matching.
@@ -520,8 +520,8 @@ do not acquire the specificity of any parent selector(s) in the ''@scope'' prelu
 	but are not scoped or otherwise affected
 	by the enclosing ''@scope'' rule.
 
-<h4 id="scope-combinator">
-Scoped Descendant Combinator</h4>
+<h3 id="scope-combinator">
+Scoped Descendant Combinator</h3>
 
 	The <dfn export>scoped descendant combinator</dfn>
 	describes a descendant relationship between two elements.