Update messages_es.properties

Commit c626fbe93b
Merge pull request #328 from AlfredoRamos/patch-1

Update messages_es.properties
Formatting
Replaced use of TB (top-bottom) with OU (over-under) since it's the more common term on the Internet
Merge branch 'master' of github.com:UniversalMediaServer/UniversalMediaServer into convert_ASS_to_ASS3D