Fix a typo

spec/mailers/notification_mailer_spec.rb

@@ -23,7 +23,7 @@ RSpec.describe NotificationMailer, type: :mailer do
         # We’re testing the (private) method `NotificationMailer#send_notification`.
         #
         # The standard trick to test a private method would be to `send(:send_notification)`, but doesn’t work here,
-        # because ActionMailer does some magic to expose public instace methods as class methods.
+        # because ActionMailer does some magic to expose public instance methods as class methods.
         # So, we use inheritance instead to make the private method public for testing purposes.
         def send_notification(dossier, template)
           super