Update ActionMailer documentation to not use deprecated template_root method...

Update ActionMailer documentation to not use deprecated template_root method as documentation, but rather raise_delivery_errors method

actionmailer/lib/action_mailer/base.rb

@@ -273,7 +273,7 @@ module ActionMailer #:nodoc:
   # = Configuration options
   #
   # These options are specified on the class level, like
-  # <tt>ActionMailer::Base.template_root = "/my/templates"</tt>
+  # <tt>ActionMailer::Base.raise_delivery_errors = true</tt>
   #
   # * <tt>default</tt> - You can pass this in at a class level as well as within the class itself as
   #   per the above section.