Remove table of contents from the README

With the top-level header, the auto-generated TOC is pretty ugly.

We could manually include a TOC, but we'd need to keep it up to date.
GitHub generates a TOC already - just hit the Outline button.

README.rst

@@ -25,8 +25,6 @@ deployment. It includes advanced identity management, auditing,
 moderation and data retention options as well as Long Term Support and
 SLAs. ESS can be used to support any Matrix-based frontend client.
 
-.. contents::
-
 🛠️ Installing and configuration
 ===============================