fix validate month and dow

In resources/d.rb, "validate_month" and "validate_dow" are both defined to take one argument, but called with two. I got the following stacktrace using version 1.3.2 of the cookbook: https://gist.github.com/jordane/7c24f606cd3a04fe490b

I got the same error and stacktrace when running from HEAD.

I opened COOK-4532 in Jira.