Fix link to CSS-CONTAIN-3 (#11266)

Author: Psychpsyo

css-conditional-5/Overview.bs

@@ -1725,7 +1725,7 @@ Additions since Level 4</h3>
 		<li>Added ''@when'' and ''@else''.
 		<li>Extended [=supports queries=] to express font capabilities
 			via ''font-tech()'' and ''font-format()''.
-		<li>Moved Container Queries from [[CSS-CONTAIN-3] to this specification.
+		<li>Moved Container Queries from [[CSS-CONTAIN-3]] to this specification.
 			(See also the [[CSS-CONTAIN-3#changes]] for more information
 			on the evolution of this feature.)
 	</ul>