chore(docs): update TOC

Author: KaseyCantu

README.md

@@ -16,7 +16,7 @@ A PHP library built on the [ShipEngine API](https://shipengine.com) offering low
 
 <!-- START doctoc generated TOC please keep comment here to allow auto update -->
 <!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
-## **Table of Contents**
+**Table of Contents**
 
 - [Quick Start](#quick-start)
 - [Examples](#examples)