Refer to internal docs for building amphora images

Easy to miss that these exist without a direct link.

Author: jovial

doc/source/operations/octavia.rst

@@ -2,6 +2,8 @@
 Octavia
 =======
 
+.. _Amphora image:
+
 Building and rotating amphora images
 ====================================
 

doc/source/operations/upgrading.rst

@@ -975,9 +975,8 @@ scope of the upgrade:
 Updating the Octavia Amphora Image
 ----------------------------------
 
-If using Octavia with the Amphora driver, you may want to `build a new amphora
-image
-<https://docs.openstack.org/octavia/latest/admin/guides/operator-maintenance.html#rotating-the-amphora-images>`__.
+If using Octavia with the Amphora driver, you should :ref:`build a new amphora
+image <Amphora image>`.
 
 Testing
 -------