ace2_inner: fix first line number position
ace2_inner: fix first line number position

Preparatory work for introducing colibris skin

aptivate/etherpad-lite,storytouch/etherpad-lite,joequant/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,ether/etherpad-lite,ether/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,aptivate/etherpad-lite,storytouch/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,aptivate/etherpad-lite,joequant/etherpad-lite,ether/etherpad-lite,joequant/etherpad-lite,cloudfoundry-community/etherpad-lite-cf,storytouch/etherpad-lite,aptivate/etherpad-lite,joequant/etherpad-lite