docs: drop deleted file from extra sphinx files

Fixes: 3e37b7e6bbad007c168a ("docs: remove plain-text copy of versions.rst")
Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5567>
diff --git a/docs/conf.py b/docs/conf.py
index 65bd4c9..e127c9e 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -120,7 +120,6 @@
   'README.UVD',
   'README.VCE',
   'README.WIN32',
-  'VERSIONS'
 ]