Removes netplan from makedepends (aarch64)

It seems that the missing cloud-init is due to this issue here with
netplan and haskell.

https://archlinuxarm.org/forum/viewtopic.php?f=4&t=16013

Removes netplan from makedepends but leave it on optdepends

PKGBUILD

@@ -31,7 +31,6 @@ depends=(
   systemd
 )
 makedepends=(
-  netplan
   python-build
   python-installer
   python-setuptools