[llvm] Update GitHub doc to mention that we accepts user branches for Stacked PRs (PR #73774)

[Mehdi Amini via llvm-commits]

https://github.com/joker-eph created https://github.com/llvm/llvm-project/pull/73774

This isn't yet a guide on how to do stacked PRs.

>From 19ca7a75a185bf30dadff048992af582a7b6106a Mon Sep 17 00:00:00 2001
From: Mehdi Amini <joker.eph at gmail.com>
Date: Wed, 29 Nov 2023 02:14:08 -0800
Subject: [PATCH] Update GitHub doc to mention that we accepts user branches
 for Stacked PR.

This isn't yet a guide on how to do stacked PRs.
---
 llvm/docs/GitHub.rst | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/llvm/docs/GitHub.rst b/llvm/docs/GitHub.rst
index 67fea9520aab6de..a89a4d955fc08b2 100644
--- a/llvm/docs/GitHub.rst
+++ b/llvm/docs/GitHub.rst
@@ -17,10 +17,11 @@ participate in the project using GitHub.
 
 Branches
 ========
-Do not create any branches in the llvm/llvm-project repository.  This repository
-is reserved for official project branches only.  We may relax this rule in
-the future if needed to support "stacked" pull request, but in that case only
-branches being used for "stacked" pull requests will be allowed.
+
+It is possible to create branches that starts with `users/<username>/`, however this is
+intended to be able to support "stacked" pull-request. Do not create any branches in the
+llvm/llvm-project repository otherwise, please use a fork (see below). User branches that
+aren't associated with a pull-request **will be deleted**.
 
 Pull Requests
 =============