When new x-maintenance-intent lint failes on CI, it errors due to GitHub perms issues

[shonfeder]

Just noticed that the check introduced in #27221 is failing rather than posting any sort of useful output (on the issue or the CI logs), apparently due to a perm issue with the github token relative to this repo. See: https://github.com/ocaml/opam-repository/actions/runs/12674982160/job/35324942586?pr=27232

I think it is addressed here: https://github.com/orgs/community/discussions/60820

cc @hannesm