chore(docs): Update tracing.md

Author: vincentkoc

docs/tracing.md

@@ -90,6 +90,7 @@ To customize this default setup, to send traces to alternative or additional bac
 
 External trace processors include:
 
+-   [Opik](https://www.comet.com/docs/opik/tracing/integrations/openai)
 -   [Braintrust](https://braintrust.dev/docs/guides/traces/integrations#openai-agents-sdk)
 -   [Pydantic Logfire](https://logfire.pydantic.dev/docs/integrations/llms/openai/#openai-agents)
 -   [AgentOps](https://docs.agentops.ai/v1/integrations/agentssdk)