[css-text-3] Fix white square bracket reference example. #8749

Author: fantasai

css-text-3/Overview.bs

@@ -5617,7 +5617,7 @@ Handling Symbols and Punctuation</h4>
 		characters [[JLREQ]];
 		thus a UA might assign these characters to a “never” prioritization level.
 		As another example, certain full-width punctuation characters
-		(such as U+301A [ LEFT WHITE SQUARE BRACKET)
+		(such as U+301A 〚 LEFT WHITE SQUARE BRACKET)
 		are considered to contain a [=justification opportunity=] in Japanese.
 		The UA might therefore assign these characters to a higher prioritization
 		level than the opportunities between ideographic characters.