Removed hack from MenuItem.
Removed hack from MenuItem.

ItemsPresenterHost now makes ItemsControls within popups a supported
scenario by default.

SuperJMN/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,susloparovdenis/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,punker76/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,OronDF343/Avalonia,grokys/Perspex,OronDF343/Avalonia,MrDaedra/Avalonia,wieslawsoltes/Perspex,susloparovdenis/Perspex,wieslawsoltes/Perspex,jkoritzinsky/Perspex,AvaloniaUI/Avalonia,susloparovdenis/Avalonia,Perspex/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,MrDaedra/Avalonia,SuperJMN/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,akrisiun/Perspex,susloparovdenis/Perspex,SuperJMN/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,Perspex/Perspex,wieslawsoltes/Perspex,jazzay/Perspex,AvaloniaUI/Avalonia