Fix branch name

Author: metaodi

CONTRIBUTING.md

@@ -29,7 +29,7 @@ flake8 --install-hook git
 
 ## Create a pull request
 
-1. Choose the `develop` branch as a target for new/changed functionality, `master` should only be targeted for urgent bugfixes.
+1. Choose the `develop` branch as a target for new/changed functionality, `main` should only be targeted for urgent bugfixes.
 2. While it's not strictly required, it's highly recommended to create a new branch on your fork for each pull request.
 3. Push to your fork and [submit a pull request][pr].
 4. Check if the [build ran successfully][ci] and try to improve your code if not.