Revert "Improve project_panel diagnostic icon knockout colors (#20760)" (#21807)

This reverts commit 571c7d4f6645528c0bf1d2bcacfd623676c69ee7.

Manually tracking the hovered entities causes issues with hightlighting:


https://github.com/user-attachments/assets/932dc022-a0ad-485c-a9db-ef03d7b86032

cc @danilo-leal @nilskch 

Release Notes:

- Fixed an issue where hovering over project panel would not update the
background correctly