Fix propose-updates job

We need to use python3, our deps are no longer installed in python.

Includes the current set of updates to the plugin registry.

Change-Id: I4753ddf60ed066cc11fa74dbbd63210dbad733a8
diff --git a/tools/generate-devstack-plugins-list.sh b/tools/generate-devstack-plugins-list.sh
index a3aa7ba..3307943 100755
--- a/tools/generate-devstack-plugins-list.sh
+++ b/tools/generate-devstack-plugins-list.sh
@@ -54,7 +54,7 @@
     cat data/devstack-plugins-registry.header
 fi
 
-sorted_plugins=$(python tools/generate-devstack-plugins-list.py)
+sorted_plugins=$(python3 tools/generate-devstack-plugins-list.py)
 
 # find the length of the name column & pad
 name_col_len=$(echo "${sorted_plugins}" | wc -L)