Update (git|review).openstack.org links to opendev

This updates links going to git.openstack.org and review.openstack.org
to go to their respective opendev locations to avoid redirects.

Change-Id: I78e3bb5303718962f591117f9c0ee11f2314b128
Closes-Bug: #1833256
diff --git a/doc/source/guides/single-machine.rst b/doc/source/guides/single-machine.rst
index cfbd6b1..a0e97ed 100644
--- a/doc/source/guides/single-machine.rst
+++ b/doc/source/guides/single-machine.rst
@@ -74,7 +74,7 @@
 .. code-block:: console
 
     $ sudo apt-get install git -y || sudo yum install -y git
-    $ git clone https://git.openstack.org/openstack-dev/devstack
+    $ git clone https://opendev.org/openstack/devstack
     $ cd devstack
 
 Run DevStack