[chore] Promote Damien Mathieu to triager role (open-telemetry#11508)

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#### Description

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Promotes @dmathieu to triager. His contributions have helped add support
for the profiling signal and have placed him [among the top 5 (non-bot)
committers in the last 6
months](https://github.com/open-telemetry/opentelemetry-collector/graphs/contributors?from=4%2F20%2F2024).

You can see a list of his contributions
[here](https://github.com/open-telemetry/opentelemetry-collector/pulls?q=is%3Apr+author%3Admathieu+).

README.md

@@ -186,6 +186,7 @@ Here is a list of community roles with current and previous members:
 - Triagers ([@open-telemetry/collector-triagers](https://github.com/orgs/open-telemetry/teams/collector-triagers)):
 
   - [Andrzej Stencel](https://github.com/andrzej-stencel), Elastic
+  - [Damien Mathieu](https://github.com/dmathieu), Elastic
   - Actively seeking contributors to triage issues
 
 - Emeritus Triagers: