Remove "usbspeed=full"

Should no longer be needed with f784824254

https://github.com/probonopd/MiniDexed/issues/39#issuecomment-1062604728

.github/workflows/build.yml

@@ -64,7 +64,8 @@ jobs:
            cp -r ./circle-stdlib/libs/circle/boot/* sdcard
            rm -rf sdcard/config*.txt sdcard/README sdcard/Makefile sdcard/armstub sdcard/COPYING.linux
            cp ./src/config.txt ./src/minidexed.ini ./src/*img sdcard/
-           echo "usbspeed=full" > sdcard/cmdline.txt
+           # echo "usbspeed=full" > sdcard/cmdline.txt
+           "" > sdcard/cmdline.txt
            cd sdcard
            cp ../kernels/* . || true
            zip -r ../MiniDexed_$GITHUB_RUN_NUMBER_$(date +%Y-%m-%d).zip *