Remove `git submodule update` call from Travis build
Remove `git submodule update` call from Travis build

I don't think this is necessary any more.

kobotoolbox/enketo-core,enketo/enketo-core,nap2000/enketo-core,medic/enketo-core,kevinmwangi/enketo-core,enketo/enketo-core,medic/enketo-core,nap2000/enketo-core,kevinmwangi/enketo-core,kobotoolbox/enketo-core,enketo/enketo-core,nap2000/enketo-core