Increase gh label list limit

[Alex-Welsh]

When listing labels using the gh, there is a default limit of 30. We have exceeded this limit in some places, which can cause the check to fail:

alex@alex-XPS-9315:~/work/skc$ gh label list -L 500 --json name --jq 'any(.name == "stackhpc-ci")'
true
alex@alex-XPS-9315:~/work/skc$ gh label list  --json name --jq 'any(.name == "stackhpc-ci")'
false

This change increases the label limit to 500