remove unnecessary Exception declaration

Change-Id: If1c86ab88987fb4ef0db8beaa412c4dc030f5520
diff --git a/utils/misc/src/main/java/org/onlab/util/NewConcurrentHashMap.java b/utils/misc/src/main/java/org/onlab/util/NewConcurrentHashMap.java
index bd17867..85a912a 100644
--- a/utils/misc/src/main/java/org/onlab/util/NewConcurrentHashMap.java
+++ b/utils/misc/src/main/java/org/onlab/util/NewConcurrentHashMap.java
@@ -3,7 +3,6 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
 
-import org.apache.commons.lang3.concurrent.ConcurrentException;
 import org.apache.commons.lang3.concurrent.ConcurrentInitializer;
 
 /**
@@ -27,7 +26,7 @@
     }
 
     @Override
-    public ConcurrentMap<K, V> get() throws ConcurrentException {
+    public ConcurrentMap<K, V> get() {
         return new ConcurrentHashMap<>();
     }
 }