Remove npm module size badge from Readme

Fixes https://github.com/sveltejs/svelte/issues/4333

README.md

@@ -7,10 +7,6 @@
     <img src="https://img.shields.io/npm/v/svelte.svg" alt="npm version">
   </a>
 
-  <a href="https://packagephobia.now.sh/result?p=svelte">
-    <img src="https://packagephobia.now.sh/badge?p=svelte" alt="install size">
-  </a>
-
   <a href="https://github.com/sveltejs/svelte/actions">
     <img src="https://github.com/sveltejs/svelte/workflows/CI/badge.svg?branch=master"
          alt="build status">