[opentelemetry-cpp] Update opentelemetry-proto dependency version to 1.3.1

[antkmsft]

Fixes #39830.

The last time when opentelemetry-cpp got updated to 1.16.0, its corresponding dependency version, opentelemetry-proto, which gets downloaded via portfile.cmake did not get updated.

But if you look at the https://github.com/open-telemetry/opentelemetry-cpp/tree/v1.16.0/third_party, the git reference for opentelemetry-proto it has, is for 1.3.1:

[antkmsft]

Closing in favor of #39823.