Fix path in CustomLayout JavaDoc (#10867)

Fixes #10866

server/src/main/java/com/vaadin/ui/CustomLayout.java

@@ -105,7 +105,7 @@ public class CustomLayout extends AbstractLayout implements LegacyComponent {
 
     /**
      * Constructor for custom layout with given template name. Template file is
-     * fetched from "<theme>/layout/<templateName>".
+     * fetched from "<theme>/layouts/<templateName>".
      */
     public CustomLayout(String template) {
         this();