docs: Remove gzip size badge (#3512)

It seems badgen/badgen.net#663 that size badge is no longer supported
so it has to be removed

README.md

@@ -5,7 +5,6 @@
 # Marked
 
 [![npm](https://badgen.net/npm/v/marked)](https://www.npmjs.com/package/marked)
-[![gzip size](https://badgen.net/badgesize/gzip/https://cdn.jsdelivr.net/npm/marked/marked.min.js)](https://cdn.jsdelivr.net/npm/marked/marked.min.js)
 [![install size](https://badgen.net/packagephobia/install/marked)](https://packagephobia.now.sh/result?p=marked)
 [![downloads](https://badgen.net/npm/dt/marked)](https://www.npmjs.com/package/marked)
 [![github actions](https://github.com/markedjs/marked/workflows/Tests/badge.svg)](https://github.com/markedjs/marked/actions)