[css-flexbox-1][editorial] Hyperlink instance of "in-flow" jargon

Erratum of #11508

Author: cvrebert

css-flexbox-1/Overview.bs

@@ -434,7 +434,7 @@ Flex Layout Box Model and Terminology</h2>
 
 	A <dfn export>flex container</dfn> is the box generated by an element with a
 	computed 'display' of ''flex'' or ''inline-flex''.
-	In-flow children of a flex container are called <dfn export lt="flex item" id="flex-item">flex items</dfn>
+	<a>In-flow</a> children of a flex container are called <dfn export lt="flex item" id="flex-item">flex items</dfn>
 	and are laid out using the flex layout model.
 
 	Unlike block and inline layout,