move chart version number update to top of MR template

.gitlab/merge_request_templates/DEFAULT.md

 Thank you for making a Merge Request. Before you merge this, please make sure
 that you:
 
+- [ ] Updated chart version number
 - [ ] Manually tested chart changes with the openappstack bootstrap script
 - [ ] Created an MR in openappstack/openappstack that applies the changes from this MR
 - [ ] Tests in that MR in openappstack/openappstack succeed
-- [ ] Updated chart version number