updated `InvalidPhoneNumberFormatException` class

src/main/java/com/zipcodewilmington/exceptions/InvalidPhoneNumberFormatException.java

@@ -1,9 +1,7 @@
 package com.zipcodewilmington.exceptions;
 
-import java.io.IOException;
-
 /**
  * Created by leon on 5/10/17.
  */ // Checked Exception
-public final class InvalidPhoneNumberFormatException extends IOException {
+public final class InvalidPhoneNumberFormatException extends Exception {
 }