[JAVA-36243] Moving jdk9 opt apis into another Optional article. (eugenp#17281)

Author: GaetanoPiazzolla

core-java-modules/core-java-optional/src/test/java/com/baeldung/java9additions/Java9OptionalUnitTest.java renamed to core-java-modules/core-java-11-2/src/test/java/com/baeldung/java9additions/Java9OptionalUnitTest.java

@@ -7,7 +7,6 @@ This module contains articles about Java Optional.
 - [Java Optional – orElse() vs orElseGet()](https://www.baeldung.com/java-optional-or-else-vs-or-else-get)
 - [Transforming an Empty String into an Empty Optional](https://www.baeldung.com/java-empty-string-to-empty-optional)
 - [Filtering a Stream of Optionals in Java](https://www.baeldung.com/java-filter-stream-of-optional)
-- [Java 9 Optional API Additions](https://www.baeldung.com/java-9-optional)
 - [Throw Exception in Optional in Java 8](https://www.baeldung.com/java-optional-throw-exception)
 - [Optional orElse Optional](https://www.baeldung.com/java-optional-or-else-optional)
 - [Uses for Optional in Java](https://www.baeldung.com/java-optional-uses)