Don’t do that.
Do this instead: https://wiki.archlinux.org/index.php/NetworkManager#Unmanaged_/etc/resolv.conf
@schnappi: When running systemd-resolved, /etc/resolv.conf is or should be a symlink to /run/systemd/resolve/stub-resolv.conf on Arch systems.
Everything is described in Arch wiki, here and here.