tdesktop: 2.1.0 -> 2.1.1

Regarding microsoft_gsl: The CMake scripts from Telegram-Desktop did not
find it anymore (I didn't investigate this) and Arch already made this
change during the last update. It's probably best to do the same here
especially since Telegram-Desktop is currently based on GSL 3.0.1 while
our version is still at 2.1.0.