Describe the bug
When I build my site locally, I get deprecation warnings about SASS darken(). (See https://sass-lang.com/documentation/breaking-changes/color-functions/.) These warnings point to just-the-docs SASS files; none of my custom SASS files include darken().

To Reproduce
Steps to reproduce the behavior:

# Clone repo
git clone https://github.com/djvill/APLS
cd APLS
git checkout -b test 74b9e6b
# Install gems
echo 'source "https://rubygems.org"' > Gemfile ; echo 'gem "just-the-docs"' >> Gemfile
bundle install
# Switch from remote_theme for GitHub to theme for local
sed -i -e 's/remote_theme:/# remote_theme:/g' -e 's/# theme:/theme:/g' _config.yml
# Build locally
bundle exec jekyll serve

Site builds correctly, but bash output includes a whole bunch of deprecation warnings:

DEPRECATION WARNING: darken() is deprecated. Suggestions:

color.scale($color, $lightness: -5.7954545455%)
color.adjust($color, $lightness: -5%)

More info: https://sass-lang.com/d/color-functions

   ╷
58 │     background-color: darken(#dcdcdc, 5%);
   │                       ^^^^^^^^^^^^^^^^^^^
   ╵
    ..\..\..\..\just-the-docs-0.10.0\_sass\buttons.scss 58:23   @import
    modules.scss 11:9                                           @import
    C:\Users\DAV49\tmp\assets\css\just-the-docs-light.scss 6:9  root stylesheet
WARNING: 25 repetitive deprecation warnings omitted.

Expected behavior
Site builds locally without warnings.

Screenshots

Desktop (please complete the following information):

• OS: Windows 10x64
• Shell: GNU bash, version 5.2.26(1)-release
• Browser: Chrome 129.0.6668.59 (Official Build) (64-bit) (cohort: Stable)

Additional context
This issue doesn't occur when I build the just-the-docs site locally, so it must be something with how my site is configured. It also didn't occur with just-the-docs version 0.7.0