ch11: [refactor] return Money instead of Franc or Dollar instance in …

…dollar() and franc() factory methods, to remove reference of Dollar and Franc constructor

src/main/java/money/Money.java

@@ -12,11 +12,11 @@ public Money(int amount, String currency) {
     }
 
     public static Money dollar(int amount) {
-        return new Dollar(amount, "USD");
+        return new Money(amount, "USD");
     }
 
     static Money franc(int amount) {
-        return new Franc(amount, "CHF");
+        return new Money(amount, "CHF");
     }
 
     public boolean equals(Object object) {