[css-ui-4][editorial] markup fix

Author: tabatkins

css-ui-4/Overview.bs

@@ -1705,7 +1705,7 @@ Controlling content selection</h3>
 	UAs should also make this content findable through their search function.
 
 	Issue: Should it also apply to ''::marker''? To <a>page-margin boxes</a>?
-	Should the [=used value=] of '''user-select/auto'' also be ''user-select/none'',
+	Should the [=used value=] of ''user-select/auto'' also be ''user-select/none'',
 	or would ''user-select/text'' be more appropriate?
 
 	The [=used value=] is the same as the [=computed value=],