[Bug]: buffers mode shows tabs too

### Is there an existing issue for this?

- [x] I have searched the existing issues

### What happened?

The issue is that I've manually set `mode = "buffers"` but I still see the tabs in the bufferline - and I see them twice

the tab is shown on the left mixed with buffers (the selected one) and on the right (the 1/2)

### What did you expect to happen?

Only show buffers and don't "mix" them. I thought that I'd have a different "set" of buffers per tab

### Config

```lua
require("bufferline").setup({
options = { always_show_bufferline = false, diagnostics = "nvim_lsp", mode = "buffers", separator_style = "slant" },
})
```

### Additional Information

_No response_

### commit

`655133c3b4c3e5e05ec549b9f8cc2894ac6f51b3`