Bump opentelemetry-api from 1.20.0 to 1.21.0

Bumps [opentelemetry-api](https://github.com/open-telemetry/opentelemetry-python) from 1.20.0 to 1.21.0.
- [Release notes](https://github.com/open-telemetry/opentelemetry-python/releases)
- [Changelog](https://github.com/open-telemetry/opentelemetry-python/blob/main/CHANGELOG.md)
- [Commits](open-telemetry/opentelemetry-python@v1.20.0...v1.21.0)

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

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

requirements-dev.txt

@@ -64,6 +64,6 @@ yapf==0.40.2
 
 std-uritemplate==0.0.46
 
-opentelemetry-api==1.20.0
+opentelemetry-api==1.21.0
 
 opentelemetry-sdk==1.20.0