Make version string optional.

versions is not yet documented for INFO.yaml
We do not yet have version in OPNFV's INFO files.

Change-Id: I1aa2f4a323fe9296bf9bfdc3a1d9043e32d24b8f
Signed-off-by: Aric Gardner <agardner@linuxfoundation.org>

info-schema

@@ -13,7 +13,6 @@ $id: 'https://github.com/lfit/releng-global-jjb/blob/master/info-schema'
 
 required:
   - 'project'
-  - 'version'
   - 'project_creation_date'
   - 'project_category'
   - 'lifecycle_state'