Improve reviewing PRs guide

This PR proposes an update to the PR review guidelines. The proposed change is about the use of the "Request changes" or the "Approve" option when finishing a PR review. Neither of these two options should be encouraged. We may want to encourage reviewers to always use "Comment", because:

- "Request changes" status is sticky and unnecessary. Placing a "/hold" should be okay because we do respect opinions from all reviewers/approvers.
  The "Request changes" status can only be discarded by people with privileges.
  We see quite a few cases where the reviewer left a "Request changes" mark and forgot to revisit a PR.
  Such a sticky status is not friendly to contributors or peer reviewers.

- The "Approve" option is confusing. It is not considered by the prow as an approval IIUC. The PR has to be approved again even if it has been "approved" this way.

Author: tengqm

content/en/docs/contribute/review/reviewing-prs.md

@@ -10,9 +10,8 @@ weight: 10
 Anyone can review a documentation pull request. Visit the [pull requests](https://github.com/kubernetes/website/pulls)
 section in the Kubernetes website repository to see open pull requests.
 
-Reviewing documentation pull requests is a
-great way to introduce yourself to the Kubernetes community.
-It helps you learn the code base and build trust with other contributors.
+Reviewing documentation pull requests is a great way to introduce yourself to the Kubernetes
+community.  It helps you learn the code base and build trust with other contributors.
 
 Before reviewing, it's a good idea to:
 
@@ -28,7 +27,6 @@ Before reviewing, it's a good idea to:
 
 Before you start a review:
 
-
 - Read the [CNCF Code of Conduct](https://github.com/cncf/foundation/blob/main/code-of-conduct.md)
   and ensure that you abide by it at all times.
 - Be polite, considerate, and helpful.
@@ -73,6 +71,7 @@ class third,fourth white
 
 Figure 1. Review process steps.
 
+
 1. Go to [https://github.com/kubernetes/website/pulls](https://github.com/kubernetes/website/pulls).
    You see a list of every open pull request against the Kubernetes website and docs.
 
@@ -103,12 +102,20 @@ Figure 1. Review process steps.
 4. Go to the **Files changed** tab to start your review.
 
    1. Click on the `+` symbol  beside the line you want to comment on.
-   1. Fill in any comments you have about the line and click either **Add single comment** (if you
-      have only one comment to make) or  **Start a review** (if you have multiple comments to make).
+   1. Fill in any comments you have about the line and click either **Add single comment**
+      (if you have only one comment to make) or **Start a review** (if you have multiple comments to make).
    1. When finished, click **Review changes** at the top of the page. Here, you can add
-      a summary of your review (and leave some positive comments for the contributor!),
-      approve the PR, comment or request changes as needed. New contributors should always
-      choose **Comment**.
+      a summary of your review (and leave some positive comments for the contributor!).
+      Please always use the "Comment"
+
+     - Avoid clicking the "Request changes" button when finishing your review.
+       If you want to block a PR from being merged before some further changes are made,
+       you can leave a "/hold" comment.
+       Mention why you are setting a hold, and optionally specify the conditions under
+       which the hold can be removed by you or other reviewers.
+
+     - Avoid clicking the "Approve" button when finishing your review.
+       Leaving a "/approve" comment is recommended most of the time.
 
 ## Reviewing checklist