travis: try newer macos version
travis: try newer macos version

beancount/fava,beancount/fava,yagebu/fava,aumayr/beancount-web,aumayr/beancount-web,beancount/fava,yagebu/fava,aumayr/beancount-web,yagebu/fava,aumayr/beancount-web,beancount/fava,beancount/fava,yagebu/fava,yagebu/fava