Remove IE8 event compatibility
Remove IE8 event compatibility

No need because admin-lte does not support IE8.

https://adminlte.io/themes/AdminLTE/documentation/index.html#browsers

osavchenko/SonataAdminBundle,mweimerskirch/SonataAdminBundle,dmarkowicz/SonataAdminBundle,ossinkine/SonataAdminBundle,greg0ire/SonataAdminBundle,OskarStark/SonataAdminBundle,mweimerskirch/SonataAdminBundle,sonata-project/SonataAdminBundle,jordisala1991/SonataAdminBundle,osavchenko/SonataAdminBundle,osavchenko/SonataAdminBundle,dmarkowicz/SonataAdminBundle,Soullivaneuh/SonataAdminBundle,jordisala1991/SonataAdminBundle,ARTACK/SonataAdminBundle,peter-gribanov/SonataAdminBundle,OskarStark/SonataAdminBundle,peter-gribanov/SonataAdminBundle,ossinkine/SonataAdminBundle,Armstrong1992/SonataAdminBundle,jordisala1991/SonataAdminBundle,Soullivaneuh/SonataAdminBundle,ARTACK/SonataAdminBundle,peter-gribanov/SonataAdminBundle,dmarkowicz/SonataAdminBundle,greg0ire/SonataAdminBundle,OskarStark/SonataAdminBundle,OskarStark/SonataAdminBundle,dmarkowicz/SonataAdminBundle,mweimerskirch/SonataAdminBundle,ossinkine/SonataAdminBundle,greg0ire/SonataAdminBundle,greg0ire/SonataAdminBundle,osavchenko/SonataAdminBundle,dmarkowicz/SonataAdminBundle,mweimerskirch/SonataAdminBundle,sonata-project/SonataAdminBundle,ossinkine/SonataAdminBundle,Soullivaneuh/SonataAdminBundle,ARTACK/SonataAdminBundle,peter-gribanov/SonataAdminBundle,jordisala1991/SonataAdminBundle,Armstrong1992/SonataAdminBundle,Soullivaneuh/SonataAdminBundle,osavchenko/SonataAdminBundle,ARTACK/SonataAdminBundle