Bumps [github.com/census-instrumentation/opencensus-proto](https://github.com/census-instrumentation/opencensus-proto) from 0.2.1 to 0.3.0.
- [Release notes](https://github.com/census-instrumentation/opencensus-proto/releases)
- [Commits](https://github.com/census-instrumentation/opencensus-proto/compare/v0.2.1...v0.3.0

)
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