docs: Adjust assistant configuration docs table of contents (#28099)

Follow up https://github.com/zed-industries/zed/pull/28088

The "Feature-specific models" was under the LM Studio section, which was
incorrect.

Release Notes:

- N/A

docs/theme/css/general.css

@@ -213,6 +213,7 @@ iframe {
 }
 
 table {
+  margin-top: 1.4rem;
   width: 100%;
   border-collapse: collapse;
   font-size: 1.4rem;