Reproduction steps:
1. Open the “TrackDeletion” project and the “SampleScene” scene
2. Using Project Browser open the “SampleTimeline“ timeline
3. In Hierarchy select the “PlayableDirector“ GameObject
4. In Timeline try to delete the Activation track

Expected result: the track can be deleted
Actual result: the track cannot be deleted

Reproduced in: 1.4.8 (2020.3.45f1), 1.6.4 (2021.3.19f1), 1.7.3 (2022.2.7f1), 1.8.1 (2020.3.45f1, 2021.3.19f1, 2022.2.7f1, 2023.1.0b5, 2023.2.0a3)

Reproduced using: macOS 13.0.1 (Intel), Windows 10 (by the reporter)

Notes:
1. Tracks can be added and edited but not deleted
2. Tracks can be deleted when enabling the “Playable Director” component, or when opening the timeline without selecting the “PlayableDirector” GameObject