readme: update table of contents

Author: vrischmann

README.md

@@ -27,11 +27,6 @@ So your mileage may vary if you try to use `zig-sqlite`.
 - [Requirements](#requirements)
 - [Features](#features)
 - [Installation](#installation)
-  - [Official package manager](#official-package-manager)
-  - [zigmod](#zigmod)
-  - [Git submodule](#git-submodule)
-  - [Using the system sqlite library](#using-the-system-sqlite-library)
-  - [Using the bundled sqlite source code file](#using-the-bundled-sqlite-source-code-file)
 - [Usage](#usage)
   - [Demo](#demo)
   - [Initialization](#initialization)