Remove unused i3 mappings to D

dotfiles/i3/config

 bindsym $mod+Shift+n            exec "$spn bmo kb next"
 bindsym $mod+Insert             exec "$spn bmo clip save"
 bindsym $mod+Shift+Insert       exec "$spn bmo clip open"
-bindsym $mod+d                  exec "xbacklight -dec 49"
-bindsym $mod+Shift+d            exec "xbacklight -inc 5"
 bindsym XF86AudioRaiseVolume    exec "$spn bmo au up"
 bindsym XF86AudioLowerVolume    exec "$spn bmo au down"
 bindsym XF86AudioMute           exec "$spn bmo au flip"