ErrorProne: fix sampler/MissingOverride

sampler/src/main/java/atlantafx/sampler/page/components/CheckBoxPage.java

@@ -63,6 +63,7 @@ public class CheckBoxPage extends AbstractPage {
     }
 
     // visually compare normal and indeterminate checkboxes size
+    @Override
     protected void onRendered() {
         var normalBox = basicCheck.lookup(".box");
         var indeterminateBox = indeterminateCheck.lookup(".box");

sampler/src/main/java/atlantafx/sampler/page/components/DatePickerPage.java

@@ -219,6 +219,7 @@ public class DatePickerPage extends AbstractPage {
 
     private static class FutureDateCell extends DateCell {
 
+        @Override
         public void updateItem(LocalDate date, boolean empty) {
             super.updateItem(date, empty);
             setDisable(empty || date.compareTo(TODAY) < 0);