fix: tests failing on rubocop rule (#448)

Author: thinkingserious

lib/sendgrid/helpers/mail/mail.rb

@@ -8,7 +8,9 @@ class Mail
     attr_reader :personalizations, :contents, :attachments, :categories, :sections, :headers, :custom_args
     attr_writer :from, :asm, :mail_settings, :tracking_settings, :reply_to
 
-    def initialize(from_email = nil, subj = nil, to_email = nil, cont = nil)
+    # We allow for all nil values here to create uninitialized Mail objects
+    # (e.g. <project-root>/use-cases/transactional-templates.md)
+    def initialize(from_email = nil, subj = nil, to_email = nil, cont = nil) # rubocop:disable Metrics/ParameterLists
       @from = nil
       @subject = nil
       @personalizations = []