Steps to reproduce:

1. In the Lighting settings window, make sure that Baked Global Illumination flag is enabled
2. Create a new area light
3. Set its shape to Disc
4. Select the Mode enum
5. Notice that Realtime, Mixed, and Baked modes are all selectable (not grayed out), while in fact they are not selectable

Notes:

- This issue only reproduces in HDRP. In Built-in RP and URP, light mode is not exposed for area lights
- Only reproduces when Baked Global Illumination flag is enabled. When it is disabled, unsupported Disc light modes are disabled (grayed out)
- One approach could be to gray out all unsupported light modes, even when Baked Global Illumination flag is enabled. This would also be a good opportunity to remove the redundant "Baked only" label
- Alternatively, remove "Mode" enum for lights which only support one mode