Allow a broader range of inputs for a UniqueFilterIterator.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/collections/trunk@1479385 13f79535-47bb-0310-9956-ffa450edef68

src/main/java/org/apache/commons/collections4/iterators/UniqueFilterIterator.java

@@ -37,7 +37,7 @@ public class UniqueFilterIterator<E> extends FilterIterator<E> {
      *
      *  @param iterator  the iterator to use
      */
-    public UniqueFilterIterator(final Iterator<E> iterator) {
+    public UniqueFilterIterator(final Iterator<? extends E> iterator) {
         super(iterator, UniquePredicate.uniquePredicate());
     }