Update CONTRIBUTING.MD (#862)

Author: reese

CONTRIBUTING.md

@@ -1,7 +1,8 @@
-# Setup
+# Contributing
 
-1. make sure you have a recent-ish rust/cargo toolchain
-2. ensure you have at least ruby 2.6 installed
+## Requirements
+
+Make sure you have a recent-ish Rust/Cargo toolchain. You can [check what version is used in CI](https://github.com/search?q=repo%3Afables-tales%2Frubyfmt%20toolchain%3A&type=code), but most recent versions should work fine.
 
 # Day to day tasks
 
@@ -13,10 +14,6 @@ in particular `cargo test --test fixtures_test` is what I use for ongoing
 development when I'm testing a new feature, which I usually start by committing
 a new fixture.
 
-## Doing what CI does:
-
-`./script/ci`
-
 ## Autoformatting
 
 Run `make fmt` to cleanup formatting for CI