docs: fix themeConfig.prism.defaultLanguage table api ref docs (#9082)

Co-authored-by: Sébastien Lorber <slorber@users.noreply.github.com>

Author: razzeee

website/docs/api/themes/theme-configuration.mdx

@@ -767,7 +767,7 @@ Accepted fields:
 | --- | --- | --- | --- |
 | `theme` | `PrismTheme` | `palenight` | The Prism theme to use for light-theme code blocks. |
 | `darkTheme` | `PrismTheme` | `palenight` | The Prism theme to use for dark-theme code blocks. |
-| `defaultLanguage` | `string` | `undefined` | The side of the navbar this item should appear on. |
+| `defaultLanguage` | `string` | `undefined` | The default language to use for code blocks not declaring any explicit language. |
 | `magicComments` | `MagicCommentConfig[]` | _see below_ | The list of [magic comments](../../guides/markdown-features/markdown-features-code-blocks.mdx#custom-magic-comments). |
 
 ```mdx-code-block