Clicking OK on challenge mode cheat dialog shows pause menu instead of leaderboards

[vrad-exe]

If you use sv_cheats on a challenge mode map, it shows a dialog indicating that you cheated and your score wasn't saved. Closing this dialog is supposed to open the leaderboards, but since a recent update, it now opens the pause menu instead due to FCVAR_CLIENTCMD_CAN_EXECUTE preventing the leaderboard open command from running. This needs to be changed to use ClientCmd_Unrestricted() so the flag is bypassed.