Clean up old & irrelevant references to Facebook (#4452)

CONTRIBUTING.md

@@ -52,20 +52,6 @@ We actively welcome your pull requests.
 5. Make sure your code lints.
 6. If you haven't already, complete the Contributor License Agreement ("CLA").
 
-## Contributor License Agreement ("CLA")
-In order to accept your pull request, we need you to submit a CLA. You only need
-to do this once to work on any of Facebook's open source projects.
-
-Complete your CLA here: <https://code.facebook.com/cla>
-
-## Issues
-We use GitHub issues to track public bugs. Please ensure your description is
-clear and has sufficient instructions to be able to reproduce the issue.
-
-Facebook has a [bounty program](https://www.facebook.com/whitehat/) for the safe
-disclosure of security bugs. In those cases, please go through the process
-outlined on that page and do not file a public issue.
-
 ## License
 By contributing to ent, you agree that your contributions will be licensed
 under the LICENSE file in the root directory of this source tree.