Remove redundant modifiers.

src/main/java/org/apache/commons/collections4/map/CompositeMap.java

@@ -504,7 +504,7 @@ public class CompositeMap<K, V> extends AbstractIterableMap<K, V> implements Ser
      * @param <K> the type of the keys in the map
      * @param <V> the type of the values in the map
      */
-    public static interface MapMutator<K, V> extends Serializable {
+    public interface MapMutator<K, V> extends Serializable {
         /**
          * Called when adding a new Composited Map results in a
          * key collision.

src/main/java/org/apache/commons/collections4/map/PassiveExpiringMap.java

@@ -159,7 +159,7 @@ public class PassiveExpiringMap<K, V>
      * @param <V> the value object type
      * @since 4.0
      */
-    public static interface ExpirationPolicy<K, V>
+    public interface ExpirationPolicy<K, V>
         extends Serializable {
 
         /**

src/main/java/org/apache/commons/collections4/set/CompositeSet.java

@@ -459,7 +459,7 @@ public class CompositeSet<E> implements Set<E>, Serializable {
     /**
      * Define callbacks for mutation operations.
      */
-    public static interface SetMutator<E> extends Serializable {
+    public interface SetMutator<E> extends Serializable {
 
         /**
          * Called when an object is to be added to the composite.