Fix jekyll-sass-converter problem

Deploying on Netlify I got:

```log
sass-embedded-1.58.3-x86_64-linux-musl requires rubygems version >= 3.3.22,
which is incompatible with the current version, 3.0.8
```log

I found the fix here:
<https://answers.netlify.com/t/rubygems-version-outdated-cannot-deploy/83652/4>

Gemfile

@@ -46,7 +46,7 @@ group :github_pages_plugins do
   gem "jekyll-redirect-from"
   # gem "jekyll-relative-links" # Not working with Jekyll 4
   # gem "jekyll-remote-theme" # I don't use a remote theme
-  gem "jekyll-sass-converter"
+  gem "jekyll-sass-converter", "~> 2.0"
   gem "jekyll-seo-tag"
   gem "jekyll-sitemap"
   # gem "jekyll-swiss" # Jekyll Theme. I don't use