fix(ci): Fixing the permission issue for the Backport workflow

[shashidhar-patil]

Summary

Backport workflow is failing due to permission issue. Found one odd secret has been used named GIT_TOKEN in this workflow as compared to other workflows.

Test Plan

Secrete GITHUB_TOKEN is being used in all different workflows and working fine.

Additional Information

• This change is backwards-breaking

[github-actions]

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[panyogesh]

LGTM