Remove `under development` warning from 0.12.0 release notes
Remove `under development` warning from 0.12.0 release notes

ehealthafrica-ci/rapidsms,catalpainternational/rapidsms,peterayeni/rapidsms,lsgunth/rapidsms,lsgunth/rapidsms,caktus/rapidsms,ehealthafrica-ci/rapidsms,eHealthAfrica/rapidsms,caktus/rapidsms,catalpainternational/rapidsms,peterayeni/rapidsms,peterayeni/rapidsms,eHealthAfrica/rapidsms,lsgunth/rapidsms,peterayeni/rapidsms,catalpainternational/rapidsms,lsgunth/rapidsms,ehealthafrica-ci/rapidsms,catalpainternational/rapidsms,eHealthAfrica/rapidsms,caktus/rapidsms