Remove unnecessary theme import from ConfirmDialog
Remove unnecessary theme import from ConfirmDialog

Theme import is not needed anymore as Sailfish.Silica import
provides Theme singleton.

sailfishos/sailfish-browser,alinelena/sailfish-browser,rojkov/sailfish-browser,alinelena/sailfish-browser,alinelena/sailfish-browser,sailfishos/sailfish-browser,sailfishos/sailfish-browser,sailfishos/sailfish-browser,rojkov/sailfish-browser,alinelena/sailfish-browser,sailfishos/sailfish-browser,rojkov/sailfish-browser