gnuboy: removed "--stereo=0" to get higher sound volume as it's not needed anymore

Set new source for gnuboy

FunKey/board/funkey/rootfs-overlay/usr/games/launchers/gb_launch.sh

@@ -2,7 +2,7 @@
 
 # Launch the process in background, record the PID into a file, wait
 # for the process to terminate and erase the recorded PID
-sdlgnuboy --syncrtc --stereo=0 "$1"&
+sdlgnuboy --syncrtc "$1"&
 pid record $!
 wait $!
 pid erase