Bump opentelemetry-otlp from 0.27.0 to 0.28.0

Bumps [opentelemetry-otlp](https://github.com/open-telemetry/opentelemetry-rust) from 0.27.0 to 0.28.0.
- [Release notes](https://github.com/open-telemetry/opentelemetry-rust/releases)
- [Commits](open-telemetry/opentelemetry-rust@opentelemetry-otlp-0.27.0...opentelemetry-otlp-0.28.0)

---
updated-dependencies:
- dependency-name: opentelemetry-otlp
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]