Improve the Two-factor Authentication sign-in text [ci skip]

CHANGELOG

@@ -17,6 +17,7 @@ v 8.8.0 (unreleased)
   - Files over 5MB can only be viewed in their raw form, files over 1MB without highlighting !3718
   - Add support for supressing text diffs using .gitattributes on the default branch (Matt Oakes)
   - Added multiple colors for labels in dropdowns when dups happen.
+  - Improve description for the Two-factor Authentication sign-in screen. (Connor Shea)
 
 v 8.7.2
   - The "New Branch" button is now loaded asynchronously

app/views/devise/sessions/two_factor.html.haml

@@ -4,7 +4,7 @@
       %h3 Two-factor Authentication
     .login-body
       = form_for(resource, as: resource_name, url: session_path(resource_name), method: :post) do |f|
-        = f.text_field :otp_attempt, class: 'form-control', placeholder: 'Two-factor authentication code', required: true, autofocus: true
-        %p.help-block.hint If you've lost your phone, you may enter one of your recovery codes.
+        = f.text_field :otp_attempt, class: 'form-control', placeholder: 'Two-factor Authentication code', required: true, autofocus: true
+        %p.help-block.hint Enter the code from the two-factor app on your mobile device. If you've lost your device, you may enter one of your recovery codes.
         .prepend-top-20
           = f.submit "Verify code", class: "btn btn-save"