[css-inline-3] Fix broken tag (w3c#10625)

Author: alkorlos

css-inline-3/Overview.bs

@@ -2568,7 +2568,7 @@ Ancestor Inlines</h4>
 	and subsequent content.
 
 <h4 id="initial-letter-multi-line">
-Multi-line Initial Letters</h4
+Multi-line Initial Letters</h4>
 
 	If an initial letter is too long to fit on one line,
 	it wraps (according to the usual text-wrapping rules),