remove support for canton-network-node in operator flux config

[isegall-da]

Was used at some point during the transition period when we had clusters in both.

Originally I thought I'd keep it around (just update to Splice) in order to support operator deployments directly from Splice, but since we're not actively testing it, I doubt it will remain working for long (if it even is currently). I propose we drop it, and consider adding back if there's a great need for it.

[ Might require backporting to 0.3.21 for HDM tests, I'll look at its usage more carefully on Monday, i.e. whether it's ever invoked from the base branch in HDM tests ]

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[isegall-da]

Might require backporting I modified it to be backward compatible, so that in canton-network-internal we can continue setting canton-network-internal there, and that will just be silently ignored in the cncluster script. In #1062 we will remove support for that, and stop passing that argument.