Sliding Sync: Prevent duplicate tags being added to traces (#17655)

Prevent duplicate tags being added to traces.

Noticed because we see these warnings in Jaeger:

<img width="462" alt="Screenshot 2024-09-03 at 2 34 05 PM"
src="https://github.com/user-attachments/assets/6fac12ed-0074-435b-9451-eccde7e7012a">