Update MSRV badge (#1812)

Author: atouchet

README.md

@@ -5,7 +5,7 @@
 [![Build Status](https://github.com/rust-bakery/nom/actions/workflows/ci.yml/badge.svg)](https://github.com/rust-bakery/nom/actions/workflows/ci.yml)
 [![Coverage Status](https://coveralls.io/repos/github/rust-bakery/nom/badge.svg?branch=main)](https://coveralls.io/github/rust-bakery/nom?branch=main)
 [![crates.io Version](https://img.shields.io/crates/v/nom.svg)](https://crates.io/crates/nom)
-[![Minimum rustc version](https://img.shields.io/badge/rustc-1.56.0+-lightgray.svg)](#rust-version-requirements-msrv)
+[![Minimum rustc version](https://img.shields.io/badge/rustc-1.65.0+-lightgray.svg)](#rust-version-requirements-msrv)
 
 nom is a parser combinators library written in Rust. Its goal is to provide tools
 to build safe parsers without compromising the speed or memory consumption. To