Fix multiversion build

Only generate for heads of branches, not for every tag

Change-Id: I2e0a379cf725c264f675db151eadbfedbae41f76
diff --git a/conf.py b/conf.py
index a124a7b..97242aa 100644
--- a/conf.py
+++ b/conf.py
@@ -74,6 +74,10 @@
 # include only the branches matching master and sdfabric-*
 smv_branch_whitelist = r'^(master|sdfabric-.*)$'
 
+# Don't include any tags - smv docs say you can put None here, but that is broken
+# https://github.com/Holzhaus/sphinx-multiversion/issues/47
+smv_tag_whitelist = r'notags'
+
 # include all remote branches
 smv_remote_whitelist = r'^.*$'
 
@@ -255,6 +259,7 @@
 # -- options for Intersphinx extension ---------------------------------------
 
 intersphinx_mapping = {
+    'sphinx': ('https://www.sphinx-doc.org/en/master', None),
     'trellis': ('https://docs.trellisfabric.org/master', None),
     'aether': ('https://docs.aetherproject.org/master', None),
     'onf': ('https://docs.opennetworking.org/', None),