Feature Flag Specificities icons in dark mode are barely visible

[zuntrax]

Describe the bug

Feature Flag Specificities icons are displayed as black on dark gray background, making them hard to see especially in the even rows of the striped table.

Notice how the icons in the khepri_db row are barely visible.

Reproduction steps

1. Find or set up a cluster that has the khepri_db feature flag disabled (not sure if required)
2. Turn on dark mode
3. Navigate to the Admin -> Feature Flags page
4. Look at the Specificities column in the khepri_db line and notice the black icon on dark background

Expected behavior

Icons are displayed with proper contrast, like in this screenshot:

Additional context

A CSS rule that targets elements of type svg that are children of elements with class specificities_icons and applies an invert filter in deps/rabbitmq_management/priv/www/css/dark.css fixes this.

I have a working fix locally, but I'm not willing to sign a CLA, so I'm not opening a PR for now, unless contribution below the threshold of originality are exempt from the CLA requirement or there is a process for one-off CC0 contributions.