Use diamond operator

Change-Id: I9bb7e90ce7f45e65b4081a5bf85570b97e44712e
diff --git a/core/store/dist/src/main/java/org/onosproject/store/link/impl/GossipLinkStore.java b/core/store/dist/src/main/java/org/onosproject/store/link/impl/GossipLinkStore.java
index 767ede5..105c77d 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/link/impl/GossipLinkStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/link/impl/GossipLinkStore.java
@@ -62,7 +62,6 @@
 import org.slf4j.Logger;
 
 import java.io.IOException;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -551,7 +550,7 @@
      */
     private static <K, V> SetMultimap<K, V> createSynchronizedHashMultiMap() {
         return synchronizedSetMultimap(
-               Multimaps.newSetMultimap(new ConcurrentHashMap<K, Collection<V>>(),
+               Multimaps.newSetMultimap(new ConcurrentHashMap<>(),
                                        () -> Sets.newConcurrentHashSet()));
     }