DEV: Standardize session confirmation prompt (#24212)

Switches to using a dialog to confirm a session (i.e. sudo mode for
account changes where we want to be extra sure the current user is who
they say they are) to match what we do with passkeys.

spec/system/page_objects/pages/user_preferences_security.rb

@@ -9,10 +9,10 @@ module PageObjects
       end
 
       def visit_second_factor(password)
-        click_link(class: "btn-second-factor")
+        click_button "Manage Two-Factor Authentication"
 
-        find(".second-factor input#password").fill_in(with: password)
-        find(".second-factor .btn-primary").click
+        find(".dialog-body input#password").fill_in(with: password)
+        find(".dialog-body .btn-primary").click
       end
     end
   end