style(rubocop): fix all safe auto correctable offenses

app/mailers/application_mailer.rb

@@ -1,4 +1,6 @@
 class ApplicationMailer < ActionMailer::Base
-  default :from => "#{Postal.smtp_from_name} <#{Postal.smtp_from_address}>"
+
+  default from: "#{Postal.smtp_from_name} <#{Postal.smtp_from_address}>"
   layout false
+
 end