Autorebase label is not working

[shalier]

Bug description:
Autorebase is not working as Mergify has changed one of their features to be a paid feature now.

Affected area (please mark with X where applicable):

• Install [ ]
• SMI Traffic Access Policy [ ]
• SMI Traffic Specs Policy [ ]
• SMI Traffic Split Policy [ ]
• Permissive Traffic Policy [ ]
• Ingress [ ]
• Egress [ ]
• Envoy Control Plane [ ]
• CLI Tool [ ]
• Metrics [ ]
• Certificate Management [ ]
• Sidecar Injection [ ]
• Logging [ ]
• Debugging [ ]
• Tests [ ]
• Demo [ ]
• CI System [X ]

Expected behavior:

Steps to reproduce the bug (as precisely as possible):

How was OSM installed?:

Anything else we need to know?:

Environment:

• OSM version (use osm version):
• Kubernetes version (use kubectl version):
• Size of cluster (number of worker nodes in the cluster):
• Others: