Update CONTRIBUTING.MD

CONTRIBUTING.MD

@@ -16,7 +16,7 @@ We use github to host code, to track issues and feature requests, as well as acc
 
 Pull requests are the best way to propose changes to the codebase (we use [Github Flow](https://guides.github.com/introduction/flow/index.html)). We actively welcome your pull requests:
 
-1. Fork the repo and create your branch from `master`.
+1. Fork the repo and create your branch from `main`.
 2. If you've added code that should be tested, add tests.
 3. If you've changed APIs, update the documentation.
 4. Ensure the test suite passes. - Not yet made