CI: Avoid adding the `triage` label if certain labels are already added at issue creation time

[leofang]

Assumptions:

1. Only team members can add labels freely (permission issue ✔ )
2. Team members have the right knowledge for issue categories etc (label picking ✔ )

I think if priority (P0, P1, ...) and category (new feature, docs, CI, bug, ...) are both selected, we should skip tagging the triage label.