That sound like a bad idea, but I don’t have a better one, so instead of removing it, just move it to a different directory so that you can restore it should something go awry.
Or better yet:
- Disconnect/remove the Windows disc.
- Fix your boot order in the BIOS/UIEFI.
- Restore the GRUB boot loader:
5. Disconnect/remove the Manjaro disc, so that Windows can’t get its grubby hands bytes on it.
6. Install Windows on the disc.
7. Shutdown after everything’s installed.
8. Reconnect the Manjaro disc.
9. Ensure the boot order in BIOS/UEFI is correct.
10. Boot into Manjaro and follow the tutorial:
That’s how I’d do it if I was a masochist trying to dual-boot with Windows.