build: bump io.opentelemetry.semconv:opentelemetry-semconv (#3925)

Bumps [io.opentelemetry.semconv:opentelemetry-semconv](https://github.com/open-telemetry/semantic-conventions-java) from 1.28.0-alpha to 1.29.0-alpha.
- [Release notes](https://github.com/open-telemetry/semantic-conventions-java/releases)
- [Changelog](https://github.com/open-telemetry/semantic-conventions-java/blob/main/CHANGELOG.md)
- [Commits](https://github.com/open-telemetry/semantic-conventions-java/commits)

---
updated-dependencies:
- dependency-name: io.opentelemetry.semconv:opentelemetry-semconv
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

apm-agent-plugins/apm-opentelemetry/pom.xml

@@ -20,7 +20,7 @@
         to make sure that in the future we stay compatible with the previous version.
         -->
         <version.opentelemetry>1.32.0</version.opentelemetry>
-        <version.opentelemetry-semconv>1.28.0-alpha</version.opentelemetry-semconv>
+        <version.opentelemetry-semconv>1.29.0-alpha</version.opentelemetry-semconv>
 
         <maven.compiler.target>8</maven.compiler.target>
         <maven.compiler.source>8</maven.compiler.source>