fedora-coreos-base: drop nm-initrd-generator

In Fedora 31, NetworkManager includes an initrd module which replaces
the legacy dracut networking one. The key bit is here:

https://github.com/dracutdevs/dracut/blob/1fcc70fe57eea0ea658aa2de5c0044683fe85cf1/modules.d/40network/module-setup.sh#L11.

It was initially in f30 as well, but was reverted due to issues:
https://src.fedoraproject.org/rpms/NetworkManager/c/7d3054a9e366f1ebdd9d7854bf11a3069119d6da?branch=f30

(One thing that confused me at first: note that this isn't a systemd
generator, it's run via the dracut cmdline hook.)

The generator does seem to have feature parity wrt karg support:
https://github.com/NetworkManager/NetworkManager/blob/ba64c162dc471740a405f9d59e7a132f0e290078/src/initrd/nmi-cmdline-reader.c

Though I couldn't get it to work in my tests; `rd.neednet=1` does not
result in a populated `resolv.conf`, which would of course cause
Ignition to fail.

Anyway, given that we tie pretty strongly into initrd networking for
e.g. Ignition and the installer, I think I'd rather we stick with the
status quo for now, and do the transition separately from the FCOS f31
rebase.

fedora-coreos-base.yaml

@@ -54,6 +54,9 @@ remove-from-packages:
               /usr/lib/systemd/system/systemd-networkd-wait-online.service]
   - [systemd-container, /usr/lib/systemd/network/.*]
   - [systemd-udev, /usr/lib/systemd/network/.*]
+  # We're still using the legacy dracut network module for now. Dracut keys off
+  # of this: https://github.com/dracutdevs/dracut/blob/1fcc70fe57eea0ea658aa2de5c0044683fe85cf1/modules.d/40network/module-setup.sh#L11
+  - [NetworkManager, /usr/libexec/nm-initrd-generator]
 
 
 remove-files: