[css-inline-3] Fix start/end mixup. #8314

Author: fantasai

css-inline-3/Overview.bs

@@ -1391,7 +1391,7 @@ Half-Leading Control: the 'leading-trim' property</h3>
 			there is no effect.
 
 			For [=inline boxes=]:
-			trims the [=block-end=] side of the box
+			trims the [=block-start=] side of the box
 			to match its [=content edge=] to the metric specified by 'text-edge'
 			(treating ''text-edge/leading'' as ''text-edge/text'').