Fix creating new labels

[yosifkit]

For some reason, pull-request: write is no longer enough to create new labels (https://github.com/orgs/community/discussions/156181), so issues: write is necessary even though the documentation still shows that pull-requests write should be enough 😓 (https://docs.github.com/en/rest/issues/labels?apiVersion=2022-11-28#create-a-label).

(Unknown if pull-request: write would now not be necessary on the apply-labels job)