kbd doesn't work as intend when used as a variable

Bug description

In 1.3, I could include a {{< kbd ... >}} within the _variables.yml file and use {{< var ... >}} with it. Now, in both 1.4 and 1.5, it doesn't work as previously.

Steps to reproduce

Create a new simple Quarto Project with RStudio.

In the index.qmd file, include:

---
title: "test"
---

{{< var test >}}

{{< kbd mac=Cmd-Shift-P win=Ctrl-Shift-P linux=Ctrl-Shift-P >}}

In the _variables.yml file, include:

test: '{{< kbd mac=Cmd-Shift-P win=Ctrl-Shift-P linux=Ctrl-Shift-P >}}'

And render it.

Expected behavior

It should print something like Ctrl-Shift-P twice (in this example).

Actual behavior

Instead it looks like:

mac=Cmd-Shift-P

Ctrl-Shift-P

Your environment

• RStudio 2023.06
• Quarto 1.5 (and tried on 1.4 as well)
• Ubuntu 22.04

Quarto check output

Quarto 1.5.31
[✓] Checking versions of quarto binary dependencies...
      Pandoc version 3.1.13: OK
      Dart Sass version 1.70.0: OK
      Deno version 1.41.0: OK
      Typst version 0.11.0: OK
[✓] Checking versions of quarto dependencies......OK
[✓] Checking Quarto installation......OK
      Version: 1.5.31
      Path: /opt/quarto/bin

[✓] Checking tools....................OK
      TinyTeX: v2023.05
      Chromium: (not installed)

[✓] Checking LaTeX....................OK
      Using: TinyTex
      Path: /home/luke/.TinyTeX/bin/x86_64-linux
      Version: 2023

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

[✓] Checking Python 3 installation....OK
      Version: 3.10.12
      Path: /usr/bin/python3
      Jupyter: (None)

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

[✓] Checking R installation...........OK
      Version: 4.4.0
      Path: /usr/lib/R
      LibPaths:
        - /home/luke/R/x86_64-pc-linux-gnu-library/4.4
        - /usr/local/lib/R/site-library
        - /usr/lib/R/site-library
        - /usr/lib/R/library
      knitr: 1.46
      rmarkdown: 2.26

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

Reproduce the issue with the provided index.qmd and _variables.yml examples using Quarto 1.4 or 1.5, then compare the rendered variable and direct kbd output. Done means the variable renders the same platform-specific shortcut as the direct kbd usage, such as Ctrl-Shift-P, without exposing the mac= value.