chore: update CODEOWNERS (#465)

## Summary
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Update the `CODEOWNERS` file to reflect the new team name.
## Change Type
- [ ] Bug fix
- [ ] New feature
- [x] Non-functional (chore, refactoring, docs)
- [ ] Performance


## How did you test this PR?
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N/A
## References

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.github/CODEOWNERS

@@ -1,5 +1,5 @@
-# Currently, Agent Metrics owns all code in this repository.
-* @DataDog/agent-metrics
+# Currently, Agent Metric Pipelines owns all code in this repository.
+* @DataDog/agent-metric-pipelines
 
 # We publish public ADP-bundled Agent images based on CI triggered through this repository,
 # and the code ownership arrangement is to ensure that Agent Delivery has a stake in the configuration