_content/doc/contribute: document new Hold label

Code-Review -2 is replaced by Hold +1.
Also update for recent review changes requiring two Google employees.

For golang/go#16764.
For golang/go#40699.

Change-Id: I6bf575e39309fdb0e25b5f741c39c71f23011334
Reviewed-on: https://go-review.googlesource.com/c/website/+/403054
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
diff --git a/_content/doc/contribute.html b/_content/doc/contribute.html
index 4b7af5f..46eef2a 100644
--- a/_content/doc/contribute.html
+++ b/_content/doc/contribute.html
@@ -924,44 +924,48 @@
 <h3 id="votes">Voting conventions</h3>
 
 <p>
-As they near a decision, reviewers will make a "vote" on your change.
-The Gerrit voting system involves an integer in the range -2 to +2:
+As they near a decision, reviewers will apply a Code-Review “vote” to your change.
+There are two possible votes:
 </p>
 
 <ul>
 	<li>
 	<b>+2</b> The change is approved for being merged.
-	Only Go maintainers can cast a +2 vote.
+	Only Go maintainers (also referred to as “approvers”) can cast a +2 vote.
 	</li>
 	<li>
 	<b>+1</b> The change looks good, but either the reviewer is requesting
 	minor changes before approving it, or they are not a maintainer and cannot
 	approve it, but would like to encourage an approval.
 	</li>
-	<li>
-	<b>-1</b> The change is not good the way it is but might be fixable.
-	A -1 vote will always have a comment explaining why the change is unacceptable.
-	</li>
-	<li>
-	<b>-2</b> The change is blocked by a maintainer and cannot be approved.
-	Again, there will be a comment explaining the decision.
-	</li>
 </ul>
 
 <p>
-At least two maintainers must approve of the change, and at least one
-of those maintainers must +2 the change.
-The second maintainer may cast a vote of Trust+1, meaning that the
-change looks basically OK, but that the maintainer hasn't done the
-detailed review required for a +2 vote.
+To be submitted, a change must have a Code-Review +2 from a maintainer.
+</p>
+
+<p>
+Maintainers can also apply a Hold +1 vote to the change,
+to mark a change that should not be submitted now
+(for example, because the <a href="/s/proposal-process">proposal review</a>
+for new API in the change has not completed).
+</p>
+
+<p>
+To be submitted, a change must not have any Hold +1 votes from a maintainer.
+</p>
+
+<p>
+Finally, to be submitted, a change must have the involvement of two Google employees,
+either as the uploader of the change or as a reviewer voting at least Code-Review +1.
+This requirement is for compliance and supply chain security reasons.
 </p>
 
 <h3 id="submit">Submitting an approved change</h3>
 
 <p>
-After the code has been +2'ed and Trust+1'ed, an approver will
-apply it to the master branch using the Gerrit user interface.
-This is called "submitting the change".
+When a change is ready, a maintainer will submit the change,
+which adds it as a commit to the Gerrit repository.
 </p>
 
 <p>
@@ -986,7 +990,6 @@
 submission.
 </p>
 
-
 <h3 id="more_information">More information</h3>
 
 <p>