Fixed up existing TextBox tests.
Fixed up existing TextBox tests.

Some tests were leaking services.

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