Fix broken Docker link in README (gchq#2250)

Author: am-periphery

README.md

@@ -24,7 +24,7 @@ Cryptographic operations in CyberChef should not be relied upon to provide secur
 
 **Prerequisites**
 
-- [Docker](hhttps://www.docker.com/products/docker-desktop/)
+- [Docker](https://www.docker.com/products/docker-desktop/)
   - Docker Desktop must be open and running on your machine