Change the GIT_BASE default to https://opendev.org

Change-Id: Ifcfce490edb3d77e4e436e002d35bc909e1a057c
diff --git a/stackrc b/stackrc
index 3432fb6..4fc31a3 100644
--- a/stackrc
+++ b/stackrc
@@ -237,7 +237,7 @@
 # ------------
 
 # Base GIT Repo URL
-GIT_BASE=${GIT_BASE:-https://git.openstack.org}
+GIT_BASE=${GIT_BASE:-https://opendev.org}
 
 # The location of REQUIREMENTS once cloned
 REQUIREMENTS_DIR=$DEST/requirements