Clarify the pull request review guidance for company diversity

As discussed at the governance/community meeting on 25/10, we clarify
the guidance on company diversity for reviews. This update upholds that
company diversity is an important recommendation that should be observed
when appropriate, not a policy that is applied to all pull requests. We
rely on maintainer discretion to determine when appropriate.

This is to ensure that we don't further slow down reviews in the project
when we have already gathered diverse input on the change in a TEP, or
the change is minor and reversible.

process/README.md

@@ -129,9 +129,9 @@ The configuration for this automation is in
 _More on the Prow process in general
 [is available in the k8s docs](https://github.com/kubernetes/community/blob/master/contributors/guide/owners.md#the-code-review-process)._
 
-The Tekton community promotes company diversity as a best practice for pull request.
-This means that, where possible, one of the reviewers of a pull request and the author
-should be affiliated to different organizations.
+The Tekton community promotes company diversity as a best practice for pull requests.
+We encourage for large or significant changes, by maintainer discretion, that pull
+requests receive feedback from multiple organizations.
 
 This best practice may not be applicable by all Tekton projects, please check the
 guidelines on a project specific details for more details.