PR label checker incorrectly complains about label missing in pytorch-probot.yml

[jithunnair-amd]

Example: pytorch/pytorch#165699 (comment)

Warning: Unknown label ciflow/rocm-navi31.
Currently recognized labels are
...

However, the PR had already added ciflow/rocm-navi31 to pytorch-probot.yml and was even able to kick off the workflow. It looks like the label checker logic needs to look at the pytorch-probot.yml file in the PR branch as opposed to main maybe?