Update project file for Avalonia.UnitTests to use net47 instead of net461
Update project file for Avalonia.UnitTests to use net47 instead of net461

wieslawsoltes/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,MrDaedra/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,grokys/Perspex,MrDaedra/Avalonia,Perspex/Perspex,jkoritzinsky/Avalonia,Perspex/Perspex,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,akrisiun/Perspex,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,grokys/Perspex,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,SuperJMN/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,jkoritzinsky/Perspex