docs(README): remove extraction from TOC

Author: char0n

README.md

@@ -39,7 +39,6 @@ Server Object URL Templating defined in following OpenAPI specification versions
 - [Getting started](#getting-started)
   - [Installation](#installation)
   - [Usage](#usage)
-    - [Extraction](#extraction)
     - [Parsing](#parsing)
     - [Validation](#validation)
     - [Substitution](#substitution)