Update CONTRIBUTING.md

Author: ar1ja

CONTRIBUTING.md

@@ -36,10 +36,6 @@ again.
      separate branches in order to ensure that a pull request only includes the
      commits related to that bug or feature.
 
-  1. Any significant changes should almost always be accompanied by tests. The
-     project already has good test coverage, so look at some of the existing
-     tests (in the `vroom/` directory) if you're unsure how to go about it.
-
   1. Do your best to have [well-formed commit messages][] for each change.
      This provides consistency throughout the project, and ensures that commit
      messages are able to be formatted properly by various git tools.