Some dark variants are deprecated in Bootstrap 5.3 and replaced by the usage of the scopable data-bs-theme attribute.
Components templates had been updated when possible to start using this feature.
The navbar_nav component had a dark prop which goals was to only be transmitted from the navbar to the dropdown component in case the navbar was in dark mode.
As only putting the data-bs-theme="dark" attribute on the navbar allows to automatically style dropdowns inside the navbar, this allowed to remove a preprocess pattern hook (One step further in the preparation of SDC/UI Patterns 2 compatibility) and remove the need of the navbar_nav component to handle a dark prop.
In case you have custom code handling the dark prop on the navbar_nav component, you can inject the data-bs-theme in its attributes instead.