[css-inline-3] Don't export inline formatting context until later. Fixes #5209

Author: fantasai

css-inline-3/Overview.bs

@@ -85,7 +85,7 @@ Inline Layout Model</h2>
 
 	In <dfn>inline layout</dfn>,
 	a mixed, recursive stream of text and [=inline-level boxes=]
-	forming an <dfn export>inline formatting context</dfn> within a [=block container=]
+	forming an <dfn>inline formatting context</dfn> within a [=block container=]
 	are laid out by [=fragmenting=] them into a stack of [=line boxes=],
 	and aligning the text and boxes to each other within each [=line box=].