fix(datepicker): fix popup CSS
fix(datepicker): fix popup CSS

Closes #5258

benhalverson/bootstrap,wesleycho/bootstrap,icfantv/bootstrap,Servoy/bootstrap,deeg/bootstrap,292388900/bootstrap,shootermv/bootstrap,icfantv/bootstrap,looker/bootstrap,Foxandxss/bootstrap,looker/bootstrap,benhalverson/bootstrap,292388900/bootstrap,Foxandxss/bootstrap,fpipita/bootstrap,RobJacobs/bootstrap,infowrap/bootstrap,Kpler/bootstrap,burlhock/bootstrap,mabi/bootstrap,Servoy/bootstrap,caoruiy/bootstrap,BookingBug/bootstrap,christor/bootstrap,angular-ui/bootstrap,benhalverson/bootstrap,vfiles/bootstrap,RobJacobs/bootstrap,BookingBug/bootstrap,byronigoe/bootstrap,burlhock/bootstrap,Kpler/bootstrap,deeg/bootstrap,shootermv/bootstrap,mabi/bootstrap,vfiles/bootstrap,angular-ui/bootstrap,caoruiy/bootstrap,fpipita/bootstrap,benhalverson/bootstrap,wesleycho/bootstrap,infowrap/bootstrap,christor/bootstrap,byronigoe/bootstrap