Sometimes Rich tables don't render headers as headers

e.g. from `pipcheckold`

See https://github.com/Textualize/rich-cli/issues/29

Desirable:

![image](https://github.com/user-attachments/assets/10c2fe1f-3de8-49a3-be5f-ba9b8a6e7c0a)

Undesirable:

![image](https://github.com/user-attachments/assets/406946fe-3326-4bbe-abd3-6b771eaf4f78)
