Group usb does not exist, use plugdev instead

--- a/mod_usb3380/udev/50-xtrx-usb3380.rules
+++ b/mod_usb3380/udev/50-xtrx-usb3380.rules
@@ -1 +1 @@
-SUBSYSTEMS=="usb", ATTRS{idVendor}=="0525", ATTRS{idProduct}=="3380", GROUP="usb", MODE="0666"
+SUBSYSTEMS=="usb", ATTRS{idVendor}=="0525", ATTRS{idProduct}=="3380", GROUP="plugdev", MODE="0666"
