Virtual Job should not need a step

[VonnyJap]

What happened:

Having a validation error when virtual job does not contain a step. See below.

What you expected to happen:

Virtual job should not need a step since it is a no-op and execution is skipped.

How to reproduce it:

shared:
  image: node:14


jobs:
  triggering-ci:
    requires: [ ~pr, ~commit ]
    steps:
        - init: echo 'init'
  ci-setup-virtual:
    requires: [ ~triggering-ci ]
    annotations:
      screwdriver.cd/virtualJob: true

Paste the config above in validator.