docs: Note the getsentry merge in the frontend docs (#13021)

Author: ryan953

develop-docs/frontend/index.mdx

@@ -4,11 +4,13 @@ description: How we write frontend code at Sentry.
 sidebar_order: 60
 ---
 
-This guide specifically focuses on the frontend part of the [Sentry](https://github.com/getsentry/sentry) and [Getsentry](https://github.com/getsentry/getsentry) codebases. It assumes you are using the eslint rules outlined by [eslint-config-sentry](https://github.com/getsentry/eslint-config-sentry); hence code style enforced by these linting rules will not be discussed here.
+This guide specifically focuses on the frontend part of the [Sentry](https://github.com/getsentry/sentry).
 
 ## Directory structure
 
-The frontend codebase is currently located under `static/app` in sentry and `static/getsentry` in getsentry.
+The frontend codebase is currently located under `static/app`.
+
+As of March 2025 `static/gsApp` and `static/gsAdmin` have been open-sourced and merged into [Sentry](https://github.com/getsentry/sentry). If you are looking for earlier git history of those folders you need to have access to [Getsentry](https://github.com/getsentry/getsentry).
 
 ## Folder & File structure