Pass appcat_namespace in push-spks make target

[mdnix]

No description provided.

[Kidswiss]

Maybe a bit more context what's broken and what this fixes :D

[TheBigLee]

LGTM. As simon says, a bit more context would be good for future reference

[mdnix]

LGTM. As simon says, a bit more context would be good for future reference

Ah yes my bad.
I had to make this change because the syn-appcat namespace no longer exists for the spks target. Instead we have to pass the namespace spks-crossplane for the things we usually use syn-appcat for. For the other make targets it will still be set to syn-appcat by default which is defined as a global variable here: vshn/kindev#40