Config to set table classes for computational table

Bug description

By default, a computational table is small, striped, and has a border. By adding the class plain it only has a border (see #2997). But it is not possible to remove the border by adding the class borderless:

Steps to reproduce

---
title: "Test"
format:
  html:
    df-print: kable
---

```{r}
#| classes: ".plain .borderless"

mtcars |>
  head(n = 10)
```

(Also, it seems inconsistent that classes requires dots, whereas class-output doesn't.)

Expected behavior

No horizontal border between rows.

Actual behavior

There is a horizontal border between rows.

Your environment

• RStudio 2024.04.2+764.pro1 "Chocolate Cosmos" Release (653611509504ac6640465e42d455d05dce98e1c4, 2024-06-05) for Ubuntu Focal
  Mozilla/5.0 (X11; Linux x86_64; rv:134.0) Gecko/20100101 Firefox/134.0, Quarto 1.6.39 (/opt/quarto/bin/quarto)
• Ubuntu 20.04.6 LTS

Quarto check output

Quarto 1.6.39
[✓] Checking environment information...
      Quarto cache location: /home/r155953/.cache/quarto
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.4.0: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.46.3: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.6.39
      Path: /opt/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: (not installed)
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: Installation From Path
      Path: /usr/bin
      Version: 2019

[✓] Checking basic markdown render....OK

[✓] Checking Python 3 installation....OK
      Version: 3.8.17
      Path: /tmp/Rtmpg1QFlO/rstudio/terminal/python3
      Jupyter: (None)

      Jupyter is not available in this Python installation.
      Install with python3 -m pip install jupyter

[✓] Checking R installation...........OK
      Version: 4.4.2
      Path: /opt/R/4.4.2/lib/R
      LibPaths:
        - /cloud/lib/x86_64-pc-linux-gnu-library/4.4
        - /opt/R/4.4.2/lib/R/library
      knitr: 1.49
      rmarkdown: 2.29

[✓] Checking Knitr engine render......OK