Fix reference to Optional.isPresent() in ObjectUtils.isEmpty()

Closes gh-27223

spring-core/src/main/java/org/springframework/util/ObjectUtils.java

@@ -114,7 +114,7 @@ public abstract class ObjectUtils {
 	 * Determine whether the given object is empty.
 	 * <p>This method supports the following object types.
 	 * <ul>
-	 * <li>{@code Optional}: considered empty if {@link Optional#empty()}</li>
+	 * <li>{@code Optional}: considered empty if not {@link Optional#isPresent()}</li>
 	 * <li>{@code Array}: considered empty if its length is zero</li>
 	 * <li>{@link CharSequence}: considered empty if its length is zero</li>
 	 * <li>{@link Collection}: delegates to {@link Collection#isEmpty()}</li>