fix(docs): Updated legal info due to migration from CLA to DCO (#10501)

* Updated legal info due to migration from CLA to DCO

Signed-off-by: hbelmiro <helber.belmiro@gmail.com>

* Updated DCO link

Signed-off-by: hbelmiro <helber.belmiro@gmail.com>

---------

Signed-off-by: hbelmiro <helber.belmiro@gmail.com>

CONTRIBUTING.md

@@ -3,17 +3,11 @@
 We'd love to accept your patches and contributions to this project. There are
 just a few small guidelines you need to follow.
 
-## Contributor License Agreement
+## Legal
 
-Contributions to this project must be accompanied by a Contributor License
-Agreement. You (or your employer) retain the copyright to your contribution;
-this simply gives us permission to use and redistribute your contributions as
-part of the project. Head over to <https://cla.developers.google.com/> to see
-your current agreements on file or to sign a new one.
+Kubeflow uses Developer Certificate of Origin ([DCO](https://github.com/apps/dco/)).
 
-You generally only need to submit a CLA once, so if you've already submitted one
-(even if it was for a different project), you probably don't need to do it
-again.
+Please see https://github.com/kubeflow/community/tree/master/dco-signoff-hook#signing-off-commits to learn how to sign off your commits.
 
 ## Contribution Guidelines