Deprecate v2beta1 for HPA

What does this MR do?

Updates autoscaling/v2beta1 to autoscaling/v2beta2

Why was this MR needed?

autoscaling/v2beta1 is deprecated in Kubernetes 1.19. autoscaling/v2beta2 is the direct replacement, which has been available since 1.12, so the majority should have it by now.

What's the best way to test this MR?

Deploy a gitlab-runner using the new autoscaling API version and throw some jobs at it and wait for the HPA to do its thing. Here's an example values.yaml snippet:

hpa:
  minReplicas: 1
  maxReplicas: 10
  metrics:
  - type: Resource
    resource:
      name: cpu
      target:
        type: Utilization
        averageUtilization: 50

What are the relevant issue numbers?

#270