removed unnecessary size() method

src/main/java/gov/usgs/earthquake/nshmp/tree/LogicTree.java

@@ -26,10 +26,6 @@ public interface LogicTree<T> extends List<Branch<T>> {
   /** Return the name of this tree. */
   String name();
 
-  /** Return the number of branches in this tree. */
-  @Override
-  int size();
-
   /**
    * Return a logic tree branch corresponding to the supplied probability.
    *