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

From https://github.com/bpfman/bpfman-operator/pull/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 https://github.com/bpfman/bpfman-operator/pull/440#pullrequestreview-2839608959_