Update Credit_Card_Validator.py

couple small typos in string outputs.

Author: srafferty73

Credit_Card_Validator.py

@@ -32,7 +32,7 @@ def first_check(self):
             message = "First check : Valid in terms of length."
 
         else:
-            message = "First chek : Check Card number once again it must be of 13 or 16 digit long."
+            message = "First check : Check Card number once again it must be of 13 or 16 digits long."
         return message
 
     def validate(self):