package publish should not try publishing to separate amd64/arm64 repositories

[displague]

kubectl crossplane package publish requires three repositories to exist, for example:

• foo
• foo-amd64
• foo-arm64

This creates an operational burden on the developer and host. It would be preferable to offer a way to publish to the base repository without requiring the architecture suffix repos.

I believe the problem stems from https://github.com/upbound/build/blob/master/makelib/image.mk#L189-L203, but I am filing the issue here since this solution shouldn't have to depend on upbound/build changes.