Update triage/support label references to kind/support (#6792)

The label triage/support has been reclassified as kind/support. The
kind/* family of labels makes more logical sense, as they describe the
"kind" of thing an issue or PR is.

For more information, see the announcement email:
https://groups.google.com/g/kubernetes-dev/c/YcaJpsjjLKw/m/i15cLLx5CAAJ