[css-inline-3] Take Nat McCully's advice on ideographic character face edges.

Author: fantasai

css-inline-3/Overview.bs

@@ -1504,17 +1504,8 @@ Appendix A: Synthesizing Alignment Metrics</h2>
 
 
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-					The top edge of the below ideograph (U+4E05 “丅”)
-					and the bottom edge of the above ideograph (U+4E04 “丄”)
-					can be taken as the ideographic character face edges.
-					In the horizontal dimension,
-					the left and right edges of the nation ideograph (U+56FD “国”)
-					or reason ideograph (U+56E0 “因”)
-					can be used.
-					In all cases, the these edges should be measured
-					at their intersection with the central baseline in that axis.
-
-					Issue: What is the best character to use for the sides?
+					The bounding box of 永 (U+6C38) can be used to find
+					the ideographic character face edges.
 
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 					The top edge of the center of the Hebrew maqaf (U+05B3 “־”)