Replace deprecated Weak Reference check with designated replacement. (#765)

"This method was originally specified to test if a reference object has been cleared and enqueued but was never implemented to do this test. This method could be misused due to the inherent race condition or without an associated `ReferenceQueue`. An application relying on this method to release critical resources could cause serious performance issue. An application should use `ReferenceQueue` to reliably determine what reference objects that have been enqueued or `refersTo(null)` to determine if this reference object has been cleared."

--------

* JDK 21: "warning: [deprecation] isEnqueued() in Reference has been deprecated"

Author: blackwinter

metafacture-triples/src/test/java/org/metafacture/triples/AbstractTripleSortTest.java

@@ -77,7 +77,7 @@ public void issue192ShouldUnregisterFromTheJVMToNotCauseMemoryLeak() throws Inte
         // Wait a tiny bit since GC Thread is not immediately done in Java 8
         Thread.sleep(10);
 
-        Assert.assertTrue(weakRef.isEnqueued());
+        Assert.assertTrue(weakRef.refersTo(null));
     }
 
 }