[css-scroll-snap-1] Remove duplicate dfn text

Author: fantasai

css-scroll-snap-1/Overview.bs

@@ -616,7 +616,7 @@ Scroll Snapping Area: the 'scroll-margin' property {#scroll-margin}
     exactly as the 'margin' property does for its longhands.
 
     Values represent outsets defining the
-    <dfn export lt="scroll snap area" local-lt="snap area">scroll snap area</dfn>
+    <dfn export local-lt="snap area">scroll snap area</dfn>
     that is used for snapping this box to the snapport.
     The <a>scroll snap area</a> is determined by taking the transformed border box,
     finding its rectangular bounding box