Fix typo (doubled "the") (w3c#8579)

Author: mattbrundage

css-text-4/Overview.bs

@@ -4071,7 +4071,7 @@ Line Breaking Details</h3>
 		<li>
 			Preserved segment breaks, and--
 			regardless of the 'white-space' value--
-			any Unicode character with the the <code>BK</code> and <code>NL</code> line breaking class,
+			any Unicode character with the <code>BK</code> and <code>NL</code> line breaking class,
 			must be treated as forced line breaks.
 			[[!UAX14]]