CONTRIBUTING: don't list instructions for rice

Since we're no longer using rice for embedded data, don't list
instructions that direct people to use it when contributing.  The normal
workflow should be sufficient and correct.

Author: bk2204

CONTRIBUTING.md

@@ -25,12 +25,6 @@ would like to make that are not dependent upon each other, consider submitting
 them as separate pull requests.
 - Write a [good commit message](http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html).
 
-## Updating management templates
-0. Install go.rice with `go install github.com/GeertJohan/go.rice`
-0. Run `rice embed-go` after all template changes have been made
-0. Commit the change
-0. Submit a pull request.
-
 ## Resources
 
 - [Contributing to Open Source on GitHub](https://guides.github.com/activities/contributing-to-open-source/)