Cation adds api-review/requested when PR is labeled with api-review/reviewed

This PR illustrates the problem: https://github.com/electron/electron/pull/40301

When an API WG member has reviewed a PR and added feedback, I think we're supposed to add the `api-review/reviewed` label and remove the `api-review/requested` label. However, when we do that it looks like Cation automatically adds back the `api-review/requested` label (which triggers API WG notifications about a new PR).

If I'm understanding our API WG labeling system correctly, Cation should only be adding the `api-review/requested` label if no other api-review label (including `api-review/reviewed`) has been applied.