Removes GitHub issue triage workflow

[jeanduplessis]

Description of your changes

Removes the GitHub issue triage workflow as it is no longer used with the repo having moved from /upbound to /crossplane-contrib

I have:

• [x] Read and followed Crossplane's contribution process.
• [x] Run make reviewable to ensure this PR is ready for review.
• [ ] ~Added backport release-x.y labels to auto-backport this PR if necessary.~

How has this code been tested

N/A