Fix multiversion builds

This includes:
* Revert switch to onf-make: onf-make was never compatible with
  this repo. For now, we want to revert these changes so that the
  build can work properly again.
* Re-enable static builds: the latest updates don't require removing
  patching from voltha-system-tests or cord-tester to work. The build
  also succeeds if patching is removed, so that is a likely future
  change to those repos.
* Switch to an updated custom version of sphinx-multiversion: though
  originally forked from zdw for the purpose of making changes to the
  prep step or other functionality, none was necessary. However, the
  latest changes to the mainline sphinx-multiversion have now been
  brought into the fork, with zdw's prep additions included.

Signed-off-by: Eric Ball <eball@linuxfoundation.org>
Change-Id: I0afb08030edcae4d2e968c63ef5eb11e17085d8a
diff --git a/conf.py b/conf.py
index 13415f7..009f01c 100644
--- a/conf.py
+++ b/conf.py
@@ -60,7 +60,7 @@
 
 project = "VOLTHA Docs"
 copyright = (
-    "Copyright 2019-2024 Open Networking Foundation Contributors"
+    "Copyright 2019-2025 Open Networking Foundation Contributors"
 )
 author = "VOLTHA Contributors"
 
@@ -147,7 +147,7 @@
 #
 # This is also used if you do content translation via gettext catalogs.
 # Usually you set "language" from the command line for these cases.
-language = None
+language = "en"
 
 # The name of the Pygments (syntax highlighting) style to use.
 pygments_style = None