Docs: Theme examples get overridden by global theme settings

### Description of issue

**NOTE: this is the Gen1 11ty site and not storybook!**

The [introduction to themes](https://opensource.adobe.com/spectrum-web-components/what-is-a-theme/#a-theme-is-all-of-it) contains the following example:

Both components were likely meant to render differently, but appear to be overridden by the global theme settings for the docs. Let's fix this issue if possible, and if it's not easy to fix, either hide the output or include a brief comment in the snippet.

Start with the linked introduction-to-themes page in the Gen1 11ty site and inspect the theme example output alongside the global documentation theme settings. Done means the two examples visibly render as intended; if that cannot be fixed easily, hide the output or add a brief explanatory comment to the snippet.

Written by the indexing model from the issue text.