[refactor] Remove unnecessary declarations in observer pattern.

observer/src/main/java/com/iluwatar/generic/Observer.java

@@ -1,5 +1,6 @@
 package com.iluwatar.generic;
 
 public interface Observer<S extends Observable<S, O, A>, O extends Observer<S, O, A>, A> {
-    public void update(S subject, A argument);
+
+    void update(S subject, A argument);
 }