Update MSRV in README.

README.md

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 ![Build status](https://github.com/01mf02/jaq/workflows/Rust/badge.svg)
 [![Crates.io](https://img.shields.io/crates/v/jaq-core.svg)](https://crates.io/crates/jaq-core)
 [![Documentation](https://docs.rs/jaq-core/badge.svg)](https://docs.rs/jaq-core)
-[![Rust 1.64+](https://img.shields.io/badge/rust-1.64+-orange.svg)](https://www.rust-lang.org)
+[![Rust 1.65+](https://img.shields.io/badge/rust-1.65+-orange.svg)](https://www.rust-lang.org)
 
 jaq (pronounced /ʒaːk/, like *Jacques*[^jacques]) is a clone of the JSON data processing tool [jq].
 jaq aims to support a large subset of jq's syntax and operations.