[OSX] reset lastKeyHandled flag when performKeyEquivalent is called
[OSX] reset lastKeyHandled flag when performKeyEquivalent is called

since this indicated a key being pressed also.
wieslawsoltes/Perspex,grokys/Perspex,Perspex/Perspex,SuperJMN/Avalonia,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,akrisiun/Perspex,jkoritzinsky/Avalonia,jkoritzinsky/Avalonia,jkoritzinsky/Perspex,grokys/Perspex,jkoritzinsky/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,jkoritzinsky/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,SuperJMN/Avalonia,wieslawsoltes/Perspex,wieslawsoltes/Perspex,wieslawsoltes/Perspex,AvaloniaUI/Avalonia,AvaloniaUI/Avalonia,wieslawsoltes/Perspex,Perspex/Perspex,jkoritzinsky/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,SuperJMN/Avalonia,AvaloniaUI/Avalonia,jkoritzinsky/Avalonia,wieslawsoltes/Perspex,AvaloniaUI/Avalonia