Tweaks to 3rd place text colour and "cl_showscoreleft"

Here are a few minor tweaks to !170 (merged):

1. The text colour of the 3rd place ranking has been changed to dark brown. The shading is more consistent with the dark grey text colour that's used for 2nd place, and it works better for what's supposed to be the colour of bronze.

2. cl_showscoreleft doesn't affect the scoreboard on the server console window. I had no intention of this CVar changing it.

3. cl_showscoreleft is now used on the HUD too. In the top-right corner of the screen, it now shows "x (y to win)" when the CVar's disabled. Otherwise, it shows "x (y left)" as it always used to.

   • I also added a check so that "x (%y left)", used to show the percentage of monsters left, only appears in game modes where players earn kills, in addition to checking if sv_killallmonsters is enabled.