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 Tube
4. Select the Mode enum
5. Notice that Realtime, Mixed, and Baked modes are all selectable, and a warning is shown

Notes:

- Only reproduces when Baked Global Illumination flag is enabled. When it is disabled, unsupported Tube light modes are disabled (grayed out)
- This issue only reproduces in HDRP. In Built-in RP and URP, light mode is not exposed for area lights
- 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 "Realtime only" label
- Alternatively, remove "Mode" enum for lights which only support one mode