fix: remove outdated references in README

* lit/index.html has never existed, it was always lit/index.lit.
  The broken reference was introduced in
  24c89f4.

* lit/reference has been renamed to lit/doc in
  d0e88f6.

* The release notes have been moved to a separate repository in
  db7e408.  (Not linking it because
  it has been archived and it's not used anymore.)

* The download page has been replaced with a direct link to GitHub in
  baf28e8.

* lit/docs/resource-types/community-resources.lit has been removed in
  77c2e71.

README.md

@@ -72,11 +72,10 @@ All of the website content can be found under the [`lit/`](https://github.com/co
 The content layout for the site is qute simple, and for the most part self-explanatory. If you want to change a specific page on the website you can usually jump straight to it by looking for the `.lit` version of the page. For example you can make changes to https://concourse-ci.org/fly.html by editing `lit/fly.lit`. 
 
 * **`html/docs-header.tmpl`** L1 navigation header for the Concourse website and docs.
-* **`lit/index.html`** The Concourse Homepage
-* **`lit/reference/`** This is where you'll find most of the documentation listed under https://concourse-ci.org/reference.html
-* **`lit/release-notes/`** Release notes separated by Concourse version. These `.lit` snippets are ultimately loaded into `lit/download.lit`
-* **`lit/download.lit/`** Concourse Downloads page
-* **`lit/docs/resource-types/community-resources.lit`** A listing of Concourse community-supported resources
+* **`lit/index.lit`** The Concourse Homepage
+* **`lit/docs/`** This is where you'll find most of the documentation listed under https://concourse-ci.org/docs.html
+
+The Resource Types live in a separate repository: [concourse/resource-types](https://github.com/concourse/resource-types).
 
 # Updating the Blog Theme