Update documentation w.r.t the VERSION file in bpfman-operator

[frobware]

From #440:

However, you should also update the documentation over at https://github.com/bpfman/bpfman/blob/main/RELEASE.md

There's also an argument to be made for potentially splitting that doc into two since we've moved the operator into it's own repository.

We may as well follow the same versioning scheme for bpfman too to avoid drift (i.e bpfman 0.5.6 and bpfman-operator 0.5.7-dev)

Originally posted by @dave-tucker in #440 (review)