Merge #864: Fix Rust blog link in README

c247ed7 Fix Rust blog link in README (Bvegas882)

Pull request description:

  ## Description
  
  Replace the outdated Rust blog link in README with the stable docs homepage.
  - The current URL `https://blog.rust-lang.org/2020/02/27/Rust-1.63.0.html` has a year path that doesn’t correspond to Rust 1.63, which risks confusion or link rot.
  - The crate explicitly targets Rust 1.63 (see `Cargo.toml`), so linking to `https://doc.rust-lang.org/` provides a stable, authoritative target without implying a specific release post date.
  - No code or CI changes; documentation only.


ACKs for top commit:
  apoelstra:
    ACK c247ed7; successfully ran local tests


Tree-SHA512: f7565abc46c01f3380a9a14cbc5231888fa4e1a2cbc3e60df4e0cabcb253ece6df3aab8cf866deac3e1e0a838417200416ffc3f0315f2b09619d79a4cdf52ce8

Author: apoelstra

README.md

@@ -6,7 +6,7 @@
     <a href="https://github.com/rust-bitcoin/rust-secp256k1/blob/master/LICENSE"><img alt="CC0 1.0 Universal Licensed" src="https://img.shields.io/badge/license-CC0--1.0-blue.svg"/></a>
     <a href="https://github.com/rust-bitcoin/rust-secp256k1/actions?query=workflow%3AContinuous%20integration"><img alt="CI Status" src="https://github.com/rust-bitcoin/rust-secp256k1/workflows/Continuous%20integration/badge.svg"></a>
     <a href="https://docs.rs/secp256k1"><img alt="API Docs" src="https://img.shields.io/badge/docs.rs-secp256k1-green"/></a>
-    <a href="https://blog.rust-lang.org/2020/02/27/Rust-1.63.0.html"><img alt="Rustc Version 1.63.0+" src="https://img.shields.io/badge/rustc-1.63.0.0%2B-lightgrey.svg"/></a>
+    <a href="https://releases.rs/docs/1.63.0/"><img alt="Rustc Version 1.63.0+" src="https://img.shields.io/badge/rustc-1.63.0.0%2B-lightgrey.svg"/></a>
   </p>
 </div>