(docs) CONTRIBUTING.md: update link to CLA

Author: kenyon

CONTRIBUTING.md

@@ -114,7 +114,7 @@ respectively.
 
 ## Submitting Changes
 
-* Sign the [Contributor License Agreement](https://cla.puppet.com).
+* Sign the [Contributor License Agreement](https://cla-assistant.io/puppetlabs/).
 * Push your changes to a topic branch in your fork of the repository.
 * Submit a pull request to the repository in the puppetlabs organization.
 * Update the related Jira ticket to mark that you have submitted code and are ready
@@ -158,4 +158,4 @@ ensure the issue has been resolved.
 * [General GitHub documentation](https://help.github.com/)
 * [GitHub pull request documentation](https://help.github.com/articles/creating-a-pull-request/)
 * [puppet-dev mailing list](https://groups.google.com/forum/#!forum/puppet-dev)
-* [Puppet community slack](https://slack.puppet.com)
+* [Puppet community slack](https://slack.puppet.com)