Remove rustc version badge from readme

Author: dtolnay

README.md

@@ -1,11 +1,9 @@
-# Serde JSON   [![Build Status]][actions] [![Latest Version]][crates.io] [![Rustc Version 1.36+]][rustc]
+# Serde JSON   [![Build Status]][actions] [![Latest Version]][crates.io]
 
 [Build Status]: https://img.shields.io/github/actions/workflow/status/serde-rs/json/ci.yml?branch=master
 [actions]: https://github.com/serde-rs/json/actions?query=branch%3Amaster
 [Latest Version]: https://img.shields.io/crates/v/serde_json.svg
 [crates.io]: https://crates.io/crates/serde\_json
-[Rustc Version 1.36+]: https://img.shields.io/badge/rustc-1.36+-lightgray.svg
-[rustc]: https://blog.rust-lang.org/2019/07/04/Rust-1.36.0.html
 
 **Serde is a framework for *ser*ializing and *de*serializing Rust data structures efficiently and generically.**