Cleaning up plugin developer docs (#58596)

docs/sources/developers/plugins/_index.md

@@ -73,20 +73,10 @@ Explore the many UI components in our [Grafana UI library](https://developers.gr
 
 For inspiration, check out our [plugin examples](https://github.com/grafana/grafana-plugin-examples).
 
-### API reference
-
-Learn more about Grafana options and packages.
-
-#### Metadata
+### Metadata
 
 - [Plugin metadata]({{< relref "metadata/" >}})
 
-#### Typescript
-
-- Grafana Data
-- Grafana Runtime
-- Grafana UI
-
-#### Go
+### SDK
 
 - [Grafana Plugin SDK for Go]({{< relref "backend/grafana-plugin-sdk-for-go/" >}})