Added notes in JavaDoc of TEXTFIELD_INLINE_ICON (#11860)

* Added notes in JavaDoc of TEXTFIELD_INLINE_ICON

Fixes https://github.com/vaadin/framework/issues/10752 and https://github.com/vaadin/framework/issues/9089

server/src/main/java/com/vaadin/ui/themes/ValoTheme.java

@@ -380,6 +380,11 @@ public class ValoTheme {
     /**
      * Move the default caption icon inside the text field. Can be combined with
      * any other TextField style.
+     * <p>
+     * Note: Does not apply in FormLayout
+     * <p>
+     * Note: TextFields with inlined icons in Grid header need to be wrapped into
+     * e.g. HorizontalLayout
      */
     public static final String TEXTFIELD_INLINE_ICON = "inline-icon";