docs: remove util-hex-encoding from internals

Author: AllanZhengYP

packages/util-hex-encoding/README.md

@@ -2,9 +2,3 @@
 
 [![NPM version](https://img.shields.io/npm/v/@aws-sdk/util-hex-encoding/beta.svg)](https://www.npmjs.com/package/@aws-sdk/util-hex-encoding)
 [![NPM downloads](https://img.shields.io/npm/dm/@aws-sdk/util-hex-encoding.svg)](https://www.npmjs.com/package/@aws-sdk/util-hex-encoding)
-
-> An internal package
-
-## Usage
-
-You probably shouldn't, at least directly.