How to reproduce:
1. Create a new empty Project
2. Go into the Edit -> Project Settings -> Package Manager tab
3. Turn on "Show Dependencies" in the Advanced Settings section
4. Open the Package Manager
5. Navigate to the "Timeline" package in the Unity Registry
6. Observe dependencies of the "Timeline" package

Expected result: Timeline is independent of any Audio Package and can freely change it to 3rd party Audio Package
Actual result: Built-in Audio package is a dependency of Timeline and can't be replaced

Note: If dependencies are not visible, make sure the option to show them is turned on in the Project Settings -> Package Manager tab

Reproducible with: 1.4.8 (2020.3.17f1), 1.5.6 (2021.1.18f1), 1.6.2 (2019.4.29f1, 2021.2.0b9, 2022.1.0a5)