Revert "Standealone Operator is beta in 1.5. (#6425)" (#6460)
Revert "Standealone Operator is beta in 1.5. (#6425)" (#6460)

As per agreement in Environments WG meeting on Feb 12, 2020,
moving operator to Alpha.

This reverts commit b3713a2654fc0e4dff407772d1ffdfee78334f08.
istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io,istio/istio.io