* YMD75 rev 3: fix BACKLIGHT_PIN
Update backlight LED pin used by QMK to control the per-key backlight for YMD75 rev 3
* YMD75 rev 3: fix BACKLIGHT_PIN - fix comments
* YMD75: move BACKLIGHT_PIN definitions to the respective versions
Signed-off-by: Nathan13888 <29968201+Nathan13888@users.noreply.github.com>