Install launcher on every launch on Linux

Just like AppUserModelId on Windows

This makes the cheat code and having the function outside of private namespace unnecessary

Telegram/SourceFiles/platform/win/specific_win.h

@@ -27,9 +27,6 @@ inline bool SkipTaskbarSupported() {
 	return true;
 }
 
-inline void InstallLauncher(bool force) {
-}
-
 inline void ActivateThisProcess() {
 }